jamesbob02

I've got a 92z 350 TPI, and for a year or so now I've had trouble with it starting hard. The longer the car has sat, the harder it is to start. However, once it's started, it runs fine. I thought the fuel pump might be week, but the pressure holds during cranking.

I've found that the only effective way of starting is by "bumping" it. For example, I'll crank for one second and see if I get a fire, then release. Usually after a few bumps it will fire once and I'll let go. If I don't release, it just goes back to non-fire cranking until I kill the battery. As such, I have to keep bumping it until I can get it to fire consecutively, and then I'll hold the crank until it's started.

If the car had been started the day before, it might take only a few bumps, but when it's been weeks or months, it can easily be 20+ (assuming I don't kill the battery).

It sounds to me like my cranking spark may not be hot enough, but when it's running, combustion is aided by the existing heat in the cylinder.

Thanks in advance!

five7kid

iTrader: (14)

Get a fuel pressure reading before you start to crank. I suspect you don't have pressure until after you start cranking. The "bump" starting thing is a red herring.

I had a non-3rd gen car that was difficult to start. Turns out the fuel pump check valve was non-functioning. The system wouldn't prime properly, even though the pump was coming on with the key turned to on. Your problem may be similar, or your timed relay isn't turning the pump on.

jamesbob02

Thanks for the reply.

What sort of pressure am I looking for at:

1. Key on
2. Initial crank load
3. Cranking
4. Engine idle
5. WOT
6. Open vs Closed loop (??)

FYI, I just installed an AFPR and set it to 50psi @ idle. My understanding is stock FP is 42-44 @ idle. I boosted some for performance and a little to compensate for using lower flow rate injectors (19lb/hr Ford vs. 22lb/hr stock). The hard starting issue was not affected by this change.

Thanks!

jamesbob02

Ok this is what I observed when I hooked up the pressure gauge again:

Key On: 33psi (cold), up to 36 after repeated Key-On pressuring cycles.
38psi (hot)

Cranking: Starts at "Key On" pressure and quickly dips to 28-30 range

Idling: 40-41 with AFPR connected to vacuum
50 with AFPR disconnected and vacuum port plugged

WOT: 48 (no load; in park)


Does that sound about right? Remember I intended to have a higher FP setting anyways.

Thanks!