Fuel injectors


New member
I recently did some work on my 1980, 2.0L, MT, non-Cal. van (removed the engine and worked on the heads). After reinstalling it, I could not get it started. I checked and re-checked the engine and the ignition and fuel systems, and discovered that I was not getting any voltage (as determined with test light)at the fuel injectors when cranking the engine to start it. All other
components were fine (checked double relay, resistors, air flow meter, ignition signal to ECU). I completed the troubleshooting procedures from the Bentley manual, which indicated that the control unit was faulty as per p.24.38 and p.24.40. I installed a re-manufactured FI control unit, and
still have the same problem. Checking the FI system components again as per Bentley p.24.15, the resistence for the temp sensors was a bit high due to a cold, unheated garage, and the voltage signal from the starter (#4 and ground) was only 7 volts when cranking; all other components were within specs. The temp sensors should not stop the FI's from firing, but would the low voltage? If not the low voltage, is it possible I have somehow damaged both the old control unit and the new control unit? Is there something that I have missed or that is not listed in Bentley that would stop the unit from working?

Any comments on this issue would be greatly appreciated.

Dave Falatko

[ 06-20-2001: Message edited by: Capt. Mike ]

Capt. Mike

Since the '80 air-cooled is basically the same AFC engine as the late '70s Type II, two tests in the old Repair Manual Type 1 provide a couple of possibilities.

Injector check -- remove injector but leave connected to ring main; pull off wire from terminal 1 of ignition coil; operate starter briefly; check than no more than 2 drops leak from each injector in one minute. What this infers is that if you have broekn the lead from terminal 1 of the coil, you may have shut down the connectors.

Voltage supply at injector, checking -- remove connector from injector; connect test light to wire connector; operate starter, test light must flicker. If test light does not flicker: check double relay; check ground connection of control unit; check triggering impulse from coil terminal 1. This infers break in ground wire of the ECU, since your other tests should have already caught the double relay.

Since yours displays the symptoms of either of these two failures, it might give you a place to start. It's interesting that both have a coil terminal 1 commonality which asks if you've broken a lead, reversed leads or shorted the coil during repairs?

Never underestimate why things don't work when the battery is low -- they can defy rationale. Since many ECU functions are voltage sensitive, they may trigger other seemingly unrelated symptoms. Start with a fresh charge on the battery.
Last edited:


New member
Thanks for you help, but it turns out the problem was with the timing. I am a little embarrassed to admit that I did this, but I installed the distributor drive gear at TDC on the intake stroke instead of the compression stroke. I think I have now made every mistake I can on this engine, but it does seems to be running great now.

More importantly, the trap I fell into was checking the fuel injector firing circuit with a test light when trying to start it. According to the manual, the test light should flicker at the injector wiring when starting. I had a test light that appeared to be exactly like that shown in the manual (incandescent), and it would not light. A more extensive manual on fuel injection systems noted that this test should be performed with a LED light. A Radio Shack LED light flickered when starting, and the fuel injection system electronic control unit was good and power was going to the injectors. Retracing all my steps prior to this tracked down the problem, but I wasted a lot of time trying to correct the injector firing circuit.


Capt. Mike

Transferred from another post to consolidate same topics.

Got spark, no fire?

clementine1980 Junior Member # 1091 posted 06-20-2001 03:36 PM

I recently purchased a 1980 westy 2.0L. The guy I bought it from said that it would run but only for about 30 seconds but he hadn't started it since last august. I got it into my shop and it wouldn't fire. Starter souds great though and the fuel pump is working. Tested the coil and the distributor. Put in a new condesor and points. Tested the MPC for signal. Everything seems to be right. Timing is on. The cold start valve is woking fine. Then we pulled the injectors. They are not even dripping. Dry as a bone. I can smell gas and it would appear that it is getting all the way to the injectors, but they are not opening. Any ideas?
Last edited:

Capt. Mike

Transferred to consolidate same topic; part of post lost.

. . . from Colorado to Maryland. The tech who appears to know his VWs thinks that my injectors may be going because the CO values were drifting during the set up and with no consistency. I've been chasing an irregular performance ghost and have replaced for maintaince/age fuel filters, Aux air reg, pump, p-regulator hoses, injector seals and have checked for vacuum leaks. I have not but will soon check the spray pattern but would like to know thoughts on longevity or where else one might go in this continued sleauthing.

Thanks, Steve

Capt. Mike

Injector failure, especially all 4, is so rare as to be out of the question. Unless they have been damaged, say by contaminated fuel, injectors seem to run forever. I've got some 38 year-olds that have never been touched and I've have never had a failure in a half million miles of other Bosche equipped vehicles.

By all means do your pattern and spray tests, but I'd lean more towards an O² sensor or voltage drift on something feeding the CPU.

How were your HC readings? Bad injectors normally kill HC readings, often sending them off the charts but if they just drift with the CO, I'd look elsewhere.

Capt. Mike

Transferred from other posts to consolidate similar topics.

Fuel injector problems?

luanne Junior Member # 92 posted 06-13-2000 07:21 AM

Let me start by saying I know nothing about my VW Westy engine. I have the manual and the John Muir book and want to learn by trial and error. The current problem is that after a two hour drive where my van ran beautifully, I camped and did not start it again until I left. It started but seemed to be running a little rough. After a short time, at stops, it didn't seem to be getting enough gas and was very lethargic when taking off. I made it home and the next day started her up. It runs intermittently. When I press on the gas peddle it sometimes is smooth and than I hear a knocking on the right side on the engine and it no longer will accelerate when given gas. It dies than is difficult to get restarted. Could this be the fuel injectors or what? It is a 1980 Westy with a new engine and recent oxygen sensor repalcement. HELP Thanks.

Capt. Mike Moderator Member # 11 posted 06-17-2000 08:48 AM

Do you have the Bentley shop manual? I'm not all that impressed with the Muir book though it is usefull with the older buses.
When a problem surfaces with a definate start time that you can isolate, it's usually something that can also be backtracked to that set of events. Some of your symptoms are very much like water in the fuel. Did you fill just before camping? Any chance of rain getting in the '80's relatively unprotected fill cap?

Water would 'settle' during the camping days and then be picked up at the restart. Water in the fuel also causes (potentially destructive) knocking because it doesn't burn or compress so your piston reacting as if hitting a solid wall, which it is.

Even at today's prices, that's a relatively easy check out that can only help anyway. Drain your tank and replace the filter. Refill with a name brand of REGULAR 87 octane gas, adding a good fuel cleaner like Lubri-Moly's FI system cleaner. Although I'm not a fan of other additives, it won't hurt for a one-time add of a can of gas line anti-freeze, which is nothing more than methyl acohol that picks up any water moisture and carries it out of the lines.

Other possibilities include a sensor getting wet or perhaps a critter deciding to explore your bus. You'd be surprised at how many engines are disabled by a mud-daubber's nest or because a critter chewed or disconnected a wire or vacuum hose.

sha66y77 Junior Member # 1612 posted 07-17-2001 07:47 PM


Had a very similar problem recently with my 1980 air-cooled bus. Had a mechanic look at it give it a good tune-up change the plugs and some wiring, oil filter, gas filter (was very dirty) but didn't do the trick. After many hours of frustration, the problem still existed and left me stranded on the road twice. As soon as the engine warmed up it would just die on me, and nothing but time and cooling off could restart it and then it would run a little and warm up and die again. Gave the bus to another mechanic that works on any out of the ordinary, and happy to say has found a faulty tempeture-sensor to the injectors to be the culprit and not a pricey part I might add. Hope this might be helpful to anyone out there.

Capt. Mike

Mike Osborne Junior Member posted June 03, 2002 03:15 PM

Can anyone help me with my (1980) vanagon? My son and I just purchased it. We're trying to learn about it together. It is a California van if that makes a difference. It has 10,000 miles on a rebuilt engine. The previous owner was having problems with stauling after hot. He said it would start up after a few minutes and run fine. He finally parked it for 2 years. He could not get it to start. We took it to a shop and he replaced the plugs and fuel pump (electric). It ran well but smoked real bad. I drove it about 1 mile from the repair shop and it shut down on me. It started right up the next day but died when warmed up. I changed the oil and it was full of gasoline. Took it back to the shop and he said he thought it was bad gas, and the head gaskets were bad on 1 & 2 cylinders. There is also a wire from the relay switch harness that is grounded to the frame. This had been added. He didn't know what this was. There was oil in the gasoline again. I have removed the gas tank and am going to coat the inside as someone said that might be part of the problem? I have removed the injectors and cold start injector and they don't appear to be stuck open. The fuel pressure was tested and he said it was fine. There were two hoses to the expansion tanks that were broken. Can anyone offer some suggestions?

Capt. Mike

You need to slow down, back up and spend enought time in your Bentley to understand the relationship of the various compenents and their functions.

Gas in the oil, and the only topic I will address here, is caused by excess fuel going into the cylinders and draining into the crankcase. This fuel has to come from somewhere and the most logical, especially in the amounts & reoccruance you descirbe, is probaly due to leaking injectors putting fuel into the manifold/intake valve area and thus it leaks through open valves past the rings into the oil.

To address this you need to check out the fuel injectors per Bentley 24.7. Also check the cold start enrichment system (24.5) and the remainder of the CPU per the test sheet posted on the tech drawings link from the home page.

Smoking could be leaking valve or old & hardened valve stem seals and are covered in Cylinder Head topic under ENGINES. As are leaking head gaskets. Its probably not related to the gas in oil.

The fuel tank condition, fuel pump, filters and the like are covered in their own topics.

That you have jury-rig wiring is indicative the previous owner has probably screwed things up and we can only recommend you return to the basics and the factory set-up & wiring. The AFC system on the air-cooleds was extremely reliable and performed well.

Capt. Mike


New member
I just got a 1984 Westfalia Wolfsburg edition. I mean ... the popup top, sleeping for me, my wife, two kids, two dogs, refrigerator, stove, swivel chairs ... everything !!! Oh yeah, a heater and air conditioner too ! Quite a leap after 81 and 82 Vanagon GL's. Not that I don't love them (still have them both ... gotta love that 20 year old German engineering), but I really would like a good heater. Lately, Winter gets a bit nippy here in WNC.

We're talking cross country next year ! It was beautiful, great shape, fairly low mileage, and ran solid. I drove it home and parked it for a week. Yesterday, I filled it up with premium and drove from Sylva to Bryson City and back, about 50 miles, everything worked great. In fact, cruising down the four lane at 60 the heater was running me out of there. This morning I started it, then walked down to my office. I swear I was only gone five minutes, and when I came back, the Van wasn't running. Now it won't start at all!

I asked my wife to turn it over while I checked for spark. The coil wire (attached to the coil) sparked at the distributor when she turned it over. I would have said, 'when she cranked it', if I had been back in Oregon, but here in North Carolina 'crank' means -- START and RUN --. I also got spark when she turned it over and I had a spark plug wire connected at the distributor but off a cylinder and connected to an extra spark plug grounded to the block.

Even though I've fixed many problems with my two aircooled, which reminds me of the previous posts about starting one cold, but hesitating or even stalling after warmed up. Check, first of all, that the 'fifth injector' or cold start valve isn't leaking. Then check the "little" temperature sending unit close to the #3? cylinder, after replacing both of these it solved that flooding problem for me.

I've never tried to diagnose a fuel problem. I have the Bentley manual and will proceed trying to diagnose, but I was wondering what was the easiest way to check for fuel. I guess I come from the old school that states, if you have spark and gas there is a big bang. I'm just really not sure how to go about this when it comes to FI, the computer, and all the sensors.


p.s. I would really like to know, in an informal poll, who would rather have electric or manual windows when it comes to being as quiet as possible for that perfect bear photo. Capt. Mike I would have given almost anything to have been there !

Capt. Mike

When an engine runs great and then quits abruptly, it's not usually the fuel injectors.

Check the topics elsewhere on this site (use search engine) on the FI sensors and the fuel pump relay. The fuel pump relay is interconnected to the FI system so it's failure usually shuts down everything.

PS: If you are talking about my bear-breath story in the FOND OR FUNNY STORIES forum, I love my electric windows but the bear definately knew that sound; as soon as he heard it on the 2nd go-around, he came a running for a hand-out. I'd be just happy if they worked without the ignition, or VW at least put in an accessory position on the ignition switch to operate them!


New member
Capt. Mike thanks for the quick response. This really is nice board. A quick board protocol question tho. Should I have started a new topic with my original post -- GOT GAS? -- I realize now this may have been the thing to do.

I got your response just before I had to go to work, and was in the middle of some seat of the pants fuel diagnostics. I had disconnected the fuel line after the filter and before the pump -- gas came out --, so I reconnected it. I then disconnected the gas line after the pressure regulator and hooked another hose up to the back end of the regulator and put it in a jar. I cranked the engine a few times and checked the jar. It had quite a bit of gas in it. I also blew in the hose going back to the tank. There was a little resistance, but I heard a gurgle, so I hooked it back up. It seems to me gas is making the round trip.

I was able to read through the appropriate sections in the manual and will do a proper fuel delivery rate test (20.19) tomorrow, weather be da.ned. It seems with the flow I have, though; It (sorry, the name of the Van hasn't hit me yet) should at least fire unless the quality of the gas is extremely poor. The Van did sit for over a year outside and when I filled it up a couple of days ago it initially leaked under the tank at the gas station. I wonder if the expansion tanks could have filled with water while it was sitting? And why did it leak? Anyway by the time I drove it home, a couple of miles, there was no more leak. And I did drive it over 50 miles later that day.

If the quality of the fuel and the rate test check out, I will proceed directly to the spray pattern test (seeing is believing) (24.25).

Capt. Mike I am a little confused as to what you are calling the fuel pump relay. Is this one of the double relay's (24.32). If so, I'm a little hesitant to check because of the CAUTION on terminal 86 of adapter C. Then, later it states to connect terminal 30 and 86 of adapter C. I'll have to re-read this section a couple of more times before proceeding.

Although I was initially a bit disappointed my new van just totally quit, I am thoroughly enjoying the diagnosis process and the kindred spirits on this board.

btw ... After reading many of the posts you referred me to through searching for the keywords in your reply, I realized I do have a lot of cool tools (nothing like the proper tool for the job, eh !) and my wife not only has a new dishwasher, but a new stove, refrigerator, washer and dryer, sewing machine, vacuum cleaner, etc.

P.S. Getting back to the perfect bear photo, I wonder if the electric windows couldn't be wired to the aux battery circuit for continuous power (engine running or not)?
Last edited by a moderator:

Capt. Mike

Thanks for the kind comments. No you should never start a new topic. It is extremely rare that any question rates a new topic -- they are almost always variations of an existing topic and I'd much rather move that rare 1% true new topic than be constantly deleting the other 99%. Also, don't mix topics.

Fuel injector topic is for the fuel injection system end point only. Diagnosing problems BEFORE the fuel injection nozzles belongs on the appropriate other topics. Obviously, weak fuel pressure cannot activate the nozzles -- FI system calls for much higher flow rates and pressures than the old carb versions.

But also bear in mind the fuel injectors are electrically controlled from the FI brain-box. (24.26) which again reverts to the dual relays 24.32.


New member
Sorry it took so long in getting back. It seems it's been raining for the last month.

1. Tested the dual relay as per 24.32 everything checked out. Interestingly though, when checking the relay on adapter B (30 & 86) the test light also lit up with the ignition off. Then I found out that terminal 30 has juice as long as the battery has juice (ignition on or off)

Also, I'm a bit confused on how to check 30 & 86 on adapter C (should the multipoint connector be on or off)

2. Did a fuel flow test --> got about a half a quart of gas in 30 seconds.
3. Did a spray pattern test 24.25 --> no spray what so ever.
4. Checked for voltage at the electrical plug at the injector --> no flicker (24.26). (assuming this test is done across the two wires of an individual connector (like the photos show))
5. Checked the multi-pin connector 24.20 --> everything checked out except all of the injectors were 32 ohms, instead of 16. (didn't check 20 & 25 or 21 & 7). Decided ground was good because 7 & 25 checked out.

Finding 4 extra fuel pump relays in the glove compartment, jockey box, or in the dash (as we say around here), I decided to get out the wiring diagrams and check a bit further.

I noticed after looking at the wiring diagram on page 97.55 that the aux air regulator, the fuel pump relay, as well as the fuel pump could somehow be part of the reason all the injectors were reading high.

With the battery disconnected I put an ohmmeter across the aux air regulator plug wires and got a short. Then I disconnected the + wire to the fuel pump and tested across the aux air regulator wires again, there was no more short.

Any ideas? Am I heading in the right direction?


--- just using the virtual to enhance the physical ... ralokych ---

Capt. Mike

Go back to a basic premise. Fuel injectors don't "inject" fuel; they are valves that allow the fuel to flow at specific triggered times and also atomize the fuel into a spray. The fuel is under constant pressure in the Fuel ring main (page 24.23). An electrical signal opens the injector and allows the fuel to spray into the intake, in VW's case the intake manifold above the intake valve.

If you have pressurized fuel to the fuel ring main, the problem has to be back to the electrical signal that triggers the injector. That all 4 injectors would fail electrically is not realistic unless some excessive voltage/amperage fried them all at the same time. And that can be tested per 24.26.

Thus it's a good chance your problem is not injectors but somewhere in the fuel supply (if no fuel to fuel ring main), or the ECU electrical side. Both of which have their own topics.


New member
I am new to this site, and therefore if I post this in the wrong section, or don't ask the correct question, please forgive me.

Currently own a 90' Westy. I have owned her for almost 7 years (with very few problems). I recently encountered problem that started with symptoms similar to the Vanagon Syndrome. Had it towed to a local VW mechanic who claimed it needed new fuel injectors. Problem appeared resolved, but the "Syndrome" reappeared on a road trip. On my last trip out, I noticed fuel leaking from my engine. After opening the lid on the engine, I noticed that fuel was spraying (copiously) from one of my injectors. The fuel was emerging right where the hosing connects to the injector, not on the other end where it connects to the fuel rail. Since there is no compression clamp on this end of the hose, I thought it migh have been a faulty fuel injector, but I am starting to think otherwise. Could a clogged fuel injector cause pressure to back up, and thus cause it to leak? I realize after reading other posts on this site, that I am going to have to resolve the Vanagon Syndrome, but as far as the fuel injector is concerned, is there anyone that might have some ideas as to what could cause it to leak.

I am little nervous about the response to this after reading some of the others posted. I am a weekend mechanic, if that, with very little VW tools and/or experience, so please be easy on me.
Thank you

Capt. Mike

No, the FI system is designed for the pump to supply excess pressure to any requirement and the excess then bleed back to the tank when not required. Thus why an FI system has a return line to the tank.

The injector is just a switched (controled by EDU) 'on-off' device, sort of like opening a faucet in the house where the pressure is constant.

Thus your fuel leak was caused, probably by lousy mechanicing -- failure to properly reinstall or replace if aged hoses, not getting injector properly seated with new seal, etc.

A VERY remote possiblity is that the return to the tank has become blocked and that point just happens to be the weakest but if the engine is otherwise running, doubt it.


New member
Gas in Oil

Just wanted to post another hint with the gas in oil topic. I found that the number 4 injector on my '85 1.9L was firing when it wasn't supposed to. After some digging around and stripping the wire shields back to the computer to try and find a short, I found the contacts with the computer were loose. As I shook the wiring harness to the computer I could get the number 4 injector to release fuel. By using a small screwdriver I was able to bend the connectors back together so that they would contact the computer better.

'85 VanagonGL Westy
1.9L Wasserboxer


New member
I didn't know what other topic to put this question in. But here goes:

Upon poking around my engine compartment a few weeks ago, i noticed a disconnected hose. This hose was coming out of the front of the fuel pressure regulator. It isn't a hose carrying fuel however. Upon investigation, I discovered it was supposed to connect into the intake manifold. What exactly is the function of this hose? I didn't notice any change in performance with it unplugged. Should there be a noticable difference?


Capt. Mike

Fuel pressure regulator adjusts pressure based on intake vacuum. See Bentley 24.5 for testing; disconnected defaults to highest pressure; FI works but is now over-pressured for normal conditions which affects pressure at the injectors.