Official Fuel injection questions thread

[busdaddy]

[garyt]

But... I have strobe timed it so many times that I have my own marks on the clamp and the distributor etc for guidance. But yes, damn, I have to do all that again... LOL... oh what a pain...

[busdaddy]

[airschooled]

Do the insides of the FI bug gas tanks have the baffle/bowls like the bus FI fuel tanks do?

Thanks,
Robbie
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[busdaddy]

[airschooled]

[busdaddy]

[garyt]

The return and feed on the tank are about an inch and a half apart, but inside the tank the feed has a bend away from the return line. This bend caused me problems because a broken bit of fuel sender seal had got stuck in it lengthwise, allowing fuel through but not enough for any strain on the engine.

I've now got to wait for a new strobe from amazon, so can't report back on that yet (my old one means I have to make so many changes to the engine that I can't trust the readings). But I realize my settings have probably changed as you say bd.

- I think, as the old gas in the oil burnt away the engine has started to run better and now it is demanding the 5 ATDC rather than where it was happy at 0 TDC. But I must strobe time it. However, the problem seems to have been cured by 'slowing' the timing.

In the meantime I've cleaned the Air Flow Meter of carbon deposits with a dremel type tool and smoothed it out a bit, it has made a remarkable difference to the responsiveness of the engine. There is a small extra passageway that bypasses the air flap and is opened or closed by the Idle Mixture Screw, it is difficult to clean inside that so I left it, I can blow through it; but it does look as though it could become blocked over a long time.

LOL I expect this will also change the timing so I've got work to do...

I've heard it's possible to put on a bigger Bosch AFM from the same period, like a BMW one. Some even have the same terminals for the wiring. Has anyone done this with an FI VW?

[sawed off]

I took my afm completely apart gary its not hard. If you have the patience it wouldnt hurt. The idle bypass area was packed with dirt and the flapper bearings were dry. The top cover that screws on, all the screws were stripped. I put next bigger screws in and had to open each hole a bit before assembly as to not force screw and break housing. Then I resealed the top cover. Make sure you use neutral dry silicone NOT regular silicone. I used mag wheel cleaner on housing parts when it was completely apart and it looks new, Not painted with silver paint as many remans are. Mine was a reman that's why I think the screws were stripped. Yhe electronics I cleaned with contact cleaner and used paper to scuff wiper board and clean contacts. Then used air fuel ratio meter and set wiper arm and idle mixture. Runs so much better now.

[garyt]

Thanks sawed, very interesting and good to know someone else is doing something similar. I found electrical contact cleaner worked very well on the wiper board too.

[FGT1958]

Got the engine rebuilt on my 78 vert and have been putting the fuel injection system back on. Cleaned and tested the injectors and they are good. The AFM tested good. Got it to fire on starting fluid, so the ignition system is working after a fashion as I have not timed it. However, I am trying to trick the system to run like it is on the test stand, so I don't have all the electrical connections hooked up. The fuel pump is hooked to a switch so I can control it manually.

So now I am chasing a fuel supply issue. Injectors are good, they just aren't squirting. I've checked the harness per bentley and I am showing some resistance between the plug and the ground. Bentleys says if you have continuity the harness is bad, but I only show like 80 ohms of resistance on one wire. Before I shell out more bucks for a new (to me) harness, would you all suggest additional tests or ideas to make sure I don't have something hooked up incorrectly? Thanks!

Edit...Just tested the double relay and it is bad, so I will try a new one and see it that helps.

[busdaddy]

It depends on which wire is showing resistance, what's the terminal number in the plug?
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[sawed off]

There is a small ground wire that connects to the negative battery terminal via a spade connector. Do you have that hooked up?

[FGT1958]

Busdaddy, it is usually one side of the fuel injector connecter. I don't know that terminal number.

And yes, I have the brown spade tip wire grounded as well as the 16 and 17 terminals from the ECU.

[busdaddy]

[garyt]

What busdaddy said, or you will have to follow the length of that wire, which is a pain. I did once find a split/pulled and broken wire under the sheathing, but it was a shame to cut it off.

Today I did the timing. I got a new Innova (US) strobe light from amazon and it worked very well, very bright, although I had to use jump start cable to extend the connectors to the battery. Much much easier for me with the inductive pick up.

My timing was a little bit off, and when I turned the dizzy a bit it started popping again. Now with it set at 5 ATDC (vacuum hoses connected) I am getting exactly 32 degrees advance at about 3000 rpm, and no popping. The car seems much smoother and the vacuum can working properly too.

Thanks a lot busdaddy.

My only problem now is an occasional refusal to start first time when warm, and a buzzing from under the dash, and the fuel pump works. It does start after a few turns of the key (like it says in the manual), but it never used to do this. I have been through the wiring and I am still searching for the problem. I am using the 1975 diagrams in the Bentley but I think the seat belt interlock was deleted on later models so there are differences. I am wondering if it is something to do with the buzzer? I have a long relay on the right hand side behind the fuses, it does not seem to do anything in or out, could this be the problem? Currently the dash warning light is not working (everything else electrical works, including interior light and back up lights), but sometimes this warning light works for no apparent reason (but no buzzer) but mostly doesn't. At some point a PO must have removed the computer connector wiring, but anyway the car worked fine for ten years without it.

[smoothracer]

Hello, I am having the same problem with the fuel injectors not spraying on my 77 fuel injected 1600cc engine. I have replaced the four injectors that were in the car when I bought it with four different ones I bought used at a swap meet. I have checked all 8 injectors on the car and none of them are spraying fuel. I find it hard to believe that all eight are no good. (I suppose its possible however) I have checked the series resistance block and switched it out with another and still have no fuel spraying from the injectors.

Using a test light I have switched the key on and tested the connector that attaches to the injectors and it comes on. The test light comes on when I touch both terminals in the connector that attaches to the fuel injector, is this correct or is one a ground and one is positive power?

The double relay has been tested according to the Bentley Manual along with most all other items in the section for fuel injection.

Thanks in advance for any support and suggestions.

[busdaddy]

[smoothracer]

Thanks for the suggestions. Following your advice I went and picked up a fuel injector test kit. Attaching the gauge to the hose going to the cold start valve and cranking the motor it read about 35 to 36 PSI. I left the gauge connected for about 45 minutes and did notice a slight drop in pressure down to about 31 PSI. Is that normal or should it maintain constant pressure? I'm thinking I have a leak somewhere.

I will be testing the injectors tomorrow using the 9 volt battery. I will report the outcome of the test on each injector. I have a total of eight injectors as mentioned already so I will test all of them.

I believe I read that the distributor tells the injectors when to fire. (correct me if I'm wrong) I currently have a vacuum advance distributor on the car and was wondering if I could install a 009 distributor on the car to see if it will start or inject fuel from the injectors or are the distributors completely different due to it being a fuel injected motor. ( A guy at work has a 009 and offered to lend it to me before I spent any money on a new one to see if that's the issue)

Thanks for your time and knowledge.

[sawed off]

Yes fuel injection uses distributor side of coil to fire injectors.