F.I. problem?

[BQS4]

OK, I'm a little "dumb" on F.I., so, I need some advice. This just started on my trip back from the Nationals. My 75 Sportwagon is a stock motor'd 75 F.I. save for the Pertronix ignition. I'm getting a hesitation or skip in the lower rpm's or if on power (like moderately accelerating). I first thought one of the plugs may be fouled. I have new plugs, but, I cleaned the old ones, just to see if that was the problem. No real difference. I have been told that even though Opel injectors do work, they're not the greatest design, so, outside of replacing/cleaning the injectors, I'm at a loss for what's causing this, other then something else in the ignition system. It's not a bad skip, but, it does make one uneasy. Any ideas?

[tomking]

Well injectors is a place to check. You likely have another set, so you could have them cleaned and install them. Another thing I would consider is rotor and cap and spark plug wires. After that? I dunno.

[Aardvaark]

Gene, from personal experience, it could be the flow meter rheostat needing cleaning. If you haven't looked at the inside of one, there is a wiper arm traveling across a potentiometer variable resistor on a printed circuit board.
If the circuit board becomes dirty, prying the cover off the flow meter, and cleaning the copper pot surface with contact cleaner or brake cleaner should
solve the problem. The cover can then be resealed with clear silicon sealant.
Do not be tempted to adjust the arm tension or play with the spring tension
of the air flow paddle to make the engine run leaner or richer. You won't really
help anything doing that and could cause the pot surface to wear faster.

[anastosmotors]

Hi Gene
Try a leakage test. Make sure you do not have a burned valve.
Pete

[Paul]

I'd check the egr vacuum hose and the fuel pressure regulator and associated vacuum hose.....

Also, I'd get out the Mity-Vac and check the EGR diaphram for leaks....

You may have to remove the egr and clean out the gunk that is inside the metal tube

[bigjim5551212]

if your spark plugs are resistor plugs, they can wear internally. The outside can look good but internally they are shot.

[tekenaar]

Gene, this sounds like an electrical problem and the absolute first thing I would check is your common L-Jet system grounds - brown wires, one at the lower throttle bracket mounting bolt at the rear of the manifold - not as likely the cause - and a group of ground wires at the FI ECM behind the pass-side kick panel - the most likely place of corrosion build-up, oddly enough, and hardly ever checked!

Proper power is important, proper ground contact even more so!

[oldopelguy]

If you don't have spare injectors and stuff, I have several EFI set-ups here we can rob parts off of if need be.

[wrench459]

BQS4
Lets put a scope on the car first and then go from there.
unless you want to be a parts changer sorry sore subject.
I've been wanting to probe a 75 fuel pump for a long time.

[Sportwagon75]

Gene - I had the same problem with one of my 75 Mantas. There's an inline fuse holder near the fuse box that supplies power to the F/I. I discovered the contacts inside the fuse holder were severely corroded. I cleaned the contacts and the problem went away. I would also concur with Otto regarding good grounding lug connections. They're critical. If all else fails...go to the back of the purple 75 FSM supplement. If you've never used it before...there's a respectable troubleshooting guide there for the F/I.

[BQS4]

Originally Posted by wrench459 BQS4 Lets put a scope on the car first and then go from there. unless you want to be a parts changer sorry sore subject. I've been wanting to probe a 75 fuel pump for a long time.

Dan;
Is this scope portable, or do I need to come down to "north FL" to get hooked up?

[wrench459]

Originally Posted by BQS4 Dan; Is this scope portable, or do I need to come down to "north FL" to get hooked up?

BQS4 we still have the old monsters if you want to go that route. I think they still work its been years since the last time they've been turned on.
Portable oh yeah almost will fit in your back pocket. Don't we have a meet coming up? Or Lisa and myself could make a fun run to the other half of Ga. one weekend. Good excuse to put some miles on the GT.

[BQS4]

Originally Posted by wrench459 BQS4 we still have the old monsters if you want to go that route. I think they still work its been years since the last time they've been turned on. Portable oh yeah almost will fit in your back pocket. Don't we have a meet coming up? Or Lisa and myself could make a fun run to the other half of Ga. one weekend. Good excuse to put some miles on the GT.

The meet is not until Nov 1st, I'd like to check it out before then

[BQS4]

As a follow up to my problem....it has been solved. John Lewis (guyopel) did some quick checking and found the ground strap from the frame to the motor/trans had come loose and that was causing the hard starting after warm up, and the "skip" turned out to be the strap, blowing in the breeze and making contact with the body.

[wrench459]

Oh Gene
Why didnt you tell me about the hard to start when hot?
When we test drove the 75 there was not.......... bit tongue.....

[BQS4]

Dan;
Yes we did, but, we fired it right up, this would occur only if the car sat for about 5-10 minutes and it wouldn't start. If I let it sit for 20-30 minutes, it would start right up.