VW CIS Problem-Page 2: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Dec. 2, 2011 9:48 a.m. deveous9 Reader

I ran the fuel pump directly to the battery and tested the spray pattern of the injectors. Two injectors looked to have bad spray patterns and after some light oil soaking they sprayed fine. I also saw that two other injector seals were bad and I have replaced them. The bottom air cleaner piece was cut for some reason by the previous owner, I am looking forward to a junkyard trip to replace the airbox assembly. Think I will replace the fuel accumulator while I am messing around with the fuel system. I will also replace the fuel filter and look to see if the intake manifold gasket is leaking. With the engine running I will spray the intake manifold with starting fluid to see if it changes the idle. Anything I am leaving out????
Dec. 2, 2011 9:54 a.m. deveous9 Reader

fornetti14 wrote:

Former CIS '83 GTI owner here.

My advice - get with the local VW community and swap your CIS unit with one that you know works. I ended up bringing my car to a local VW specialist and for $250 they found two bad injectors plus the main source of my problem back then. I had a bad fuel tank. The OEM tank had a rubber baffle in the bottom that had rotted away. $160 for a new fuel tank and it ran perfect.

Oddly enough I read about the fuel tank flaw from lots of other online sources and whenever a tank went bad, a fuel accumulator also failed. I will be checking for both soon enough.
Dec. 2, 2011 9:43 p.m. Flogger00 New Reader

benzbaron wrote:

I only learned this way to check injectors from the Probst CIS troubleshooting book so it must be bull, right?

Have you ever actually tried listening to a CIS injector? Take an injector to 80psi with compressed air and then tell me it doesn't make a sound. The CIS injector do indeed produce a buzz frequency and if you haven't tried listening to them don't tell me they don't make a sound! The CIS injector uses a spring and stop valve to make sure the nozzles don't open until 20psi. When the injector opens fully you will hear the spring buzzing with fluctuations in fuel pressure.

Honestly I took my leak down tester to a spare set of injectors with compressed air. A good injector won't open until 20psi, after that the injector will open partially and start buzzing. At 80psi an injector make a hell of a buzz.

Sorry if I misunderstood your previous post. No, I never ran air through CIS injectors except to blow out / swirl around injector cleaner. I have, however, ran them in a rig similiar to deveous9's picture (except Mr. Safety here used glass jars) The only sound I heard was the fuel pump and gas splashing in the jars. With my '83 GTI running, I can't hear anything from my injectors even with my stethoscope. Maybe my injectors are quiet. Maybe my car is just too loud to hear over (quite possible). Maybe they only buzz with air and not fluid. I don't know. In any event, it sounds like the OP has verified volumes and corrected patterns, so injectors don't seem to be the issue here.
Dec. 2, 2011 10:03 p.m. benzbaron Dork

All the injectors I have are the late model(1978) ones so who knows. Bosch switched from stainless injectors to brass ones on the mercedes because the stainless ones would gall into the hard line fitting. I got a set at the junkyard and I'll be damned if I didn't find one galled into a hardline fitting. There were a few iterations on the CIS injector so maybe I'm just stuck in the past with my funky old benz. Some of the later model injectors were air shielded so maybe they don't create the buzzing the ones on the older mercedes do.

Hopefully I didn't come of harshly, CIS is a great system but I'd like to be rid of it. California won't let you megasquirt so to hell with it.
Dec. 2, 2011 11:15 p.m. Flogger00 New Reader

In reply to benzbaron:

On the surface it seemed a little harsh, but I know better. Besides, my skin's thicker than it looks. As for why yours buzz and mine don't - beats me. I'd think the internals are all so similar they'd all behave the same. Maybe it's a brass vs. stainless thing. BTW, not that it matters, but OP's '83 GTI should have non air shrouded injectors. As for galling, yeah, I'd been warned of that but never experienced it. They're tight and can be a bear to get off the lines, though. I usually break 'em free w/2 closed end wrenches and the assembly likes to tilt and twist when I try to spin them apart. Oh, and OP, off the top of my head I can't think of any purpose for the fuel accumulator except to reduce vapor lock when hot (not your problem). I assume the big hoses off the intake manifold in your picture are just temporary for access to the injectors. This one's a longshot, but I notice your big vacuum line to the brake booster is routed differently than mine, and in a way that may possible put stress on it's connection. Are your sure you've got a good seal at the booster? If not, that's a big leak and could easily cause your symptoms. Also, backing away from fuel for a quick moment - you sure the ignition timing's right?
Dec. 3, 2011 7:05 a.m. Curmudgeon SuperDork

I was just going to suggest check the brake booster for vac leaks. You might want to pull the hose and plug off the fitting on the manifold, then try it again. For some stupid reason, occasionally my '83 would backfire, this would blow the vacuum check valve out of the booster and it would run like ass until I could get over to the side of the road, raise the hood etc and reinstall the thing. In fact, several times it backfired and blew injectors out of the intake. Most times it would only pop them out an inch or so but a couple times one would come all the way out and spray fuel around the engine compartment. I finally safety wired the damn things down. But then it started blowing the booster valves out. I never could figure out what caused it to backfire.
Dec. 3, 2011 9:02 a.m. chrispy New Reader

I currently have a 87 Golf with CIS that I campaign as a GP autox car. I've been chasing CIS issues for years between this car and my old BMW. The fuel accumulator's purpose is to hold residual pressure in the system to insure easier starting. Nothing in your posts suggests its bad. I would check every hose for leaks, replace the fuel filter, replace fuel injector seals, and clean the warm up regulator. As for the cut airbox, its not affecting the car, really. Many believed that cutting the box provides a "cold air intake effect" when all it really does is provide more noise. Fix it last. I made the mistake of throwing parts on the BMW before checking the easy stuff and ended up chasing my tail to the point that I gave up on it. Buy a Bentley manual, it will save tons of headaches and lookover the bimmerforums link I posted. That link summarizes the system and how to test it very well. The parts are in different locations but they all work the same. Good luck.
Dec. 5, 2011 8:23 p.m. deveous9 Reader

Today I bypassed the fuel accumulator and ran fuel straight to the fuel distributor using new fuel lines. I also replaced all the injector seals and replaced the bottom air box. My junk yard trip was awesome because I managed to source tons of good usable parts, injectors, sensors, wiring and interior parts. Videos and pictures are going up tomorrow.
Dec. 16, 2011 3:23 p.m. deveous9 Reader

I want to thank everyone for the tips. I have found the problem, the fuel tank was deffective. After running the vehicle with a full tank the problem dissapeared! Its only when i run the car with 1/4 tank and i make right turns that i expierence problems. Went out for several test drives and now i am in the process of building a nice little track toy.