76 dying when putting in reverse.

[Fry]

Posted in the past about my 76 dying when idling and sometimes when I would hit the brake. I brought it to a mechanic and got the problem fixed. My EFI needed some tuning and it fired up and worked no problem for about 2 weeks. Yesterday for thanks giving I was going to take it out. Got it started and it sounded like it was about to die. I put it in reverse and got maybe 2 feet back and the thing died and wouldn’t start back up. I left it for about any hour came back outside and it fired right up. I wonder if somebody could lead me in the right direction to look for the problem?
It’s a 76 351W with fast efi and I recent replaced the ignition coil 2 weeks ago.
This is a video of it running this morning. When I started it up it sounded like it was gonna stutter and stall out. But this is it .

https://imgur.com/a/Je3Wxk4

 

[DirtDonk]

Is that a relatively stock engine, or does it have a pretty healthy cam in it? It certainly sounds like a lumpy lump cam, but perhaps that’s just how it sounds when it’s not running correctly?
If it’s a larger cam, you should probably be idling at a much higher RPM. Automatic transmissions don’t like it, and owners don’t always like it, but it’s a necessity with a big cam and low engine vacuum.
This also creates an issue with putting it in gear.

Where is your ignition time controlled? Is it from the computer, or is it a standalone ignition system? If standalone, does it have vacuum Advance? And if so, is it connected to full vacuum or ported vacuum?
Have you checked for vacuum leaks, using the usual methods of spraying a liquid around the entire engine area?
Does it do anything weird when you press on the brakes?

And last, but definitely not least, can you check fuel pressure to see if it’s good and consistent?

 

[Fry]

Could a radiator leak cause it to not start from a cold start.

Looks like I have a radiator leak.

https://imgur.com/a/0aMJSql

 

[DirtDonk]

No.

 

[DirtDonk]

How does it run otherwise?
Fresh build, or has some mileage on it?
What all was done to make it right this last time? Just tuning, or more?
Why did you replace the coil?

 

[Fry]

Runs fine otherwise. Has some mileage on it. Purchased 3 years ago with a lot of unknowns. 32000 miles since the frame off is what I was told. All that was done the last time was fine tuning of the FAST efi. I was told it was set too low. After that got it from the shop, drove around all afternoon. Pulled into my driveway and it died. Called up the mechanic he came out and looked at it and said it was the ignition coil. Changed it out and it worked fine for a week until I attempted to go somewhere for thanksgiving. Like I said. I put it in reverse and it died. Wouldn’t crank back up. Left and came home an hour later and it cranked right up.

 

[DirtDonk]

Thanks for the extra details. We’ve heard so many stories of running, dying, not starting, and then starting later when cool, but it’s never fallen down to just one simple cure.
Give me a description it almost sounds like a fuel delivery issue, but that certainly not guaranteed.

Is there an easy way to test fuel pressure on yours? Some kind of a Schrader valve you can slip a gauge over?
It’s not common, but it’s one of those things that every fuel injected vehicle should have permanently mounted I think. A nice easy to access fuel pressure gauge.

Good luck. Maybe somebody has more insight, but that’s all I’ve got for now.

 

[DirtDonk]

Oh, but next time it is running acceptably, check for vacuum leaks, using a spray liquid of some kind.
On old engines, my go to is carburetor cleaner or brake clean. But on an engine with fairly fresh paint, or just paint that’s nice, I wouldn’t use carburetor cleaner because it can affect the paint. Brake clean too, of course, but it evaporates more quickly.
But for that reason, on an engine that’s fairly nice, I prefer a spray bottle with water. Doesn’t hurt a thing, but still affects the idle.
You don’t care whether the idle goes up or down, you’re just looking for a change.

 

[mhinchliffe]

We'd always use a small propane torch bottle with a washer nozzle hose on it to feed a combustible gas to search for a vacuum leak. If it smoothed out and sped up the idle - bullseye, there's your leak.

 

[ba123]

Unless a large vacuum leak, I would think it's more from lack of air causing an engine to die. More air generally causes a leaner higher idle, not a low one.

I don't know the Fast EFI system but if it's anything like the way the stock system is set up, you need to set the idle screw for a minimum amount of air and then the IAC Valve (Idle Air Controller) controls how much air goes in under varying conditions. Other things that need to be right when idling and moving in and out of gear are timing and fuel.

If it was working fine for two wees and then suddenly not, mean it certainly could be a vacuum leak with the inconsistency but it more likely isn't properly tuned at idle. It might have been tuned for warmer air and now that it's colder out, it's not.

Do you have an idle screw for the valve body like stock? If so, I'd start by turning it IN 1/4 turn and see what happens but make sure to keep note of exactly where it was before you move it.