Technical Fuel pressure pressure

[dustinatcusa]

Hello, just picked up a 1982 FI spider. Having trouble keeping it running. Hopefully some awesome people out there have some insight. Looks like the external fuel pump was recently replaced. I checked the pressure just pass the pump and getting 100psi. Is that normal? Is that to high before getting to the fuel regulator? I can get the Fiat to start and idle if I punch off the return line(will die when trying to throttle it higher). I took off the old injectors. Tested to see if they open and sprayed cleaner through them while open. My next step is to replace the fuel regulator. Just not sure what the pressure from the pump should be. Thanks

 

[124BC1]

I don't have info on the FI Spiders but afaik they were fitted with a Bosch L Jetronic F.I. system - this system's fuel pressure is usually c. 3 bar, i.e. c. 45 psi.

Maybe someone has fitted a much higher output pressure fuel pump to try to cure the running issues? I don't recall the stock Bosch pump being able to generate 100 psi.
It might be a good idea to check the fuel pressure after the fuel regulator (perhaps at the fuel rail?) before deciding to replace the regulator?

Your car's symptoms do sound like fuel starvation.
Is there an inline filter in the fuel supply line (usually there is with F.I.), could this be choked? I think it's possible to have high fuel pressure but insufficient flow rate if there's a restriction somewhere.

Given the age of this car, if it happens to have been left unused for a long time with old fuel in the tank, it's possible for the very fine brass mesh/gauze filter screen on the fuel pickup pipe in the tank to have become choked, resulting in fuel starvation?
Your symptoms do indeed sound like fuel starvation?
This pickup pipe and its mesh filter screen can be inspected by removing the fuel tank gauge sender unit (pickup pipe and sender unit are one unit, easily accessible from inside the trunk, no need to drop the tank).

 

[dustinatcusa]

Thanks for the help and info. I replaced the regulator and still same issue. When I do a constant spay of starter fluid in the throttle body, I can keep it running and rev it up to 5000rpms with no issue, then dies(starved) when stop spraying starter fluid. I'm thinking the injectors aren't working right and just buy news Bosch injectors. Not sure what else to rule out. Thoughts???

 

[dustinatcusa]

Regulator pressure was 65. That should be ok.

 

[124BC1]

Have you tested the injectors for spray pattern and flow rate?
What triggers the injectors to spray more fuel when you accelerate, ecu? air meter?
Is there a moveable flap or something in the air meter (I can't remember what is used on the Bosch L Jetronic system which I think is what is used on your car) that might be sticking??

**Throttle position sensor**, I seem to remember problems with the carbon track on similar systems, resulting in the ecu not getting a signal that the throttle had been opened, so no extra fuel being injected to cause the engine to rev up.

It's going to get expensive to keep changing parts unless you've determined for certain that they're faulty.

 

[bugsymike]

I don't want to send you off in the wrong direction, but I have a Haynes manual for Audi100 that used Bosch K and KE systems up to 1987 and also a similar system Ford used up to 1985. Obviously the exact details are best , but around 1988 I was having a problem with a 350 Mercedes saloon when no data was available and I was able to use a VW Golf GTi manual which pointed me in the right direction. It was a different problem to yours, it would start, but as soon as you tried to accelerate it died, the problem was the warm up regulator which increases fuel pressure when cold..
I see in these systems they give fuel pressure up to 78psi as standard. The Audi system is on the left and the Ford one is branded Ford, but has similarities. There are several pages in these manuals regarding them, as it was in the days when Haynes manuals actually helped the DIY brigade
Please feel free to ignore these if irrelevant.