Intermittent Hard Starting 84 FI

[AJgraham02]

Hi Guys, I have an 84 Spider with the factory L Jet and Electronic ignition and I'm running into a problem where my car will just not start sometimes. I have to crank for 20 plus seconds with my foot on the floor for it to maybe catch, after which I need to keep the throttle open for it to stay running, otherwise it just dies. It all seemed to start after I hit a big nasty bump and it shut off in the middle of road and wouldn't restart. The next day it was fine.

What's strange is that it comes and goes. Some days I can drive it around town no problems, others I can't get it running long enough to back out of my driveway. I've gone through the ignition system and replaced almost all the vacuum hoses because it was sitting for a while, and every time I think its sorted a day or two later the problem is back. It might be related to temperature or moisture, but I really have no idea. I'd love to hear your guys thoughts and see about narrowing down what I might need to test

[tima01864]

I will pipe in, You hit a bump and engine died. My guess is a lost connection, I would check tightness in the FI ones. Escpecially under the intake manifold TTS connection.

[RRoller123]

+1, check all the FI connections, especially the AFM, and the Temp sensor on the coolant T up front. Disconnect that coolant T or the AFM, and the car should immediately die.

[AJgraham02]

Update. I checked the connections at the sensor in the Coolant T, which was new(replaced a while back because it was zip tied in place) and the thermo time switch which was also good. My boss suggested I unplug the cold start valve and limit the fuel, because from me describing it, it sounds like a flooding issue(me needing to mat my foot to the floor to clear it out). And that definitely helped once it was running, but after a few minutes idling it would die again.

So I'm thinking maybe too much fuel pressure or a leaking cold start valve but I will have to check tomorrow

[RRoller123]

Try running it with the gas cap removed and report back. Humor me on this, just be careful of course.

[AJgraham02]

I will give it a shot after work tonight.

The gas cap removed and everything else hooked up properly correct?

[RRoller123]

Yes. looking to see if vapor cannister blocked, tank return line blocked, improper cap fitted, etc. It will tell us a lot.

[AJgraham02]

Hi Guys, I tried to start it with the gas cap off, It fired right up but refused to idle on its own after 20-30 seconds, I needed to keep throttle pressed to keep in running.
After it died the first time i needed to crank it for quite a while before it would catch again and then it wouldn't idle at all.

Longshot, but is it possible that when i hit the bump i knocked something out of place in the AFM?

[tima01864]

Anyone know how to check pressure from the fuel pump? I am thinking a clogged filter? Guessing

[RRoller123]

Try putting a fuel pressure gauge made for FI, with a scale up to at least 40psi, on a "T" that you install off the line right at the CSI. You should have about 36 psi or thereabouts. Maybe there is a clogged line or a bad pump or filter that causes head pressure loss after a few seconds. You replaced the fuel filter?

[AJgraham02]

Yeah I replaced the filter but as part of a preventative maintenance back before this problem started. I will grab a pressure gauge tomorrow, give it a shot and report back

[AJgraham02]

I will also crawl under and double check that wires at the pump and make sure everything is still hooked up nice and tight

[RRoller123]

I believe that you can force the pump to come on, without having to start the car, by putting the ignition switch to "RUN", removing the large black air tube, and reaching inside the AFM and pushing open the door flap. This should turn on the pump in a normally wired car. Then you can read the pressure on the gauge.

(A simpler gauge setup is to just pull the FI hose from the CSI and attach the fuel gauge directly without a "T". This is not ideal, for various flow and gauge operation readings, but it will certainly yield accurate enough data for this exercise. Either way, depressurize the line first, or gas WILL spray all over the place for a moment. I just wrap a microfiber cloth towel around the line as I slowly remove it, that catches the fuel).

Note that many cars (including mine), have been rewired to turn the fuel pump on directly, i.e. when the key is in the "RUN" position. This is to bypass the dual relay so that the repair to it doesn't need to be made when it eventually fails. So if you hear the pump when you put the key into "RUN" there is no need to pull the air tube and push in the AFM door flap.

[AJgraham02]

I went to test the fuel pressure tonight. I put the pressure gauge with a T right before the cold start valve. Strange though was there was no spray of fuel. I did however take the gascap off first before touching the lines. Got it started and let it idle until it decided to die. Fuel pressure was between 30-35psi

After that initial reading I went through my L jet troubleshooting packets and it started that if pressure was below factory spec (which they have listed as 42 psi + or - 3 to pinch off the fuel return line and observe the pressure. Upon pinching off that line with the appropriate pliers pressure immediately jumped to 100 psi on the gauge, which according to the paperwork says bad fuel pressure regulator and to replace it.


On a side note... Does anyone know how to get the line for the cold start injector off the fuel rail. Age has not been its friend

[tima01864]

Search fuel line Cold start injector,