fuel pump check valve?

[jsmithcds]

Good Morning Gentlemen,

Car: 79sc 3.2ss conversion


I am busy chasing a starting problem. At the start fires immediately, stumbles around for a 3 seconds and dies. Turn the key again fires right up and runs perfect.

My first thought was leaky injector letting fuel drip out causing loss of fuel in the lines. Changed out the injectors last night which is a project I was planning on doing anyway. Good excuse to justify the $200 for new ones!! The car pushes thru the power much smoother now. I believe I found a few ponies. Car definitely pulls harder.

I did some messing with the plate and believe the mixture is dead on.

WUR is brand new 3 months ago.

AAR works good. When it fires the rpms climb up to 1750 and then drop to normal with in a minute or two. Drops to about 1k when cold. Settles in around 850 when warm.

Removed the oil cap and the car breaths a little harder like it should.

Before I get grilled about getting some CIS gauges..... They will be in my possession on Monday. Looking forward to getting intimate with my CIS as soon as possible.

So the question: I looked thru Pelican for a check valve by the fuel pump. Don't see it. Is there one?

Next step hook up some gauges.

Any other thoughts on what it could be?

Thanks for any input
Justin

[psalt]

Which distributor are you using and does it have vacuum retard ?

[jsmithcds]

The distributer does have a vac retard on it and it is hooked up.

[ossiblue]

I believe the check valve is built into the fuel pump on the 79 SC, but others can confirm this. Once you get your gauges, you can run the tests that will indicate a leaky check valve.

In the meantime, you can try this: With the engine cold, jump the terminals at the fuel pump relay so the pump will run with the ignition in the "run" position (you'll have to do this when you get your gauges and begin testing pressures, so you might as well learn it now.) Turn on the ignition, let the pump run for a few seconds, and then turn the key to "start". If it fires and runs, then the likely cause is the check valve, assuming the other fuel components--fuel distributor and wur--are o.k.

[psalt]

I have solved the same symptom on several SC's over the past 20 years and it was always a tuning issue, not something that can be fixed by part swapping. Warm up the car by driving it. Disconnect and plug the retard line on the back of the distributor (it will have vacuum at idle and the idle speed will go up). Reset the idle speed to 950 rpm. Check the idle ignition timing (5BTDC) then the high speed timing (24-28 BTDC). Unfortunately you have to wait overnight to check if the cold start stumble goes away.

[jsmithcds]

I will give that a whirl and see if that take care of it.

Thanks
Justin