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Topic: Fuel System Troubleshoot Questions (Read 558 times) previous topic - next topic

Fuel System Troubleshoot Questions

1984 Cougar, 3.8L, TBI
Fuel Pressure s/b 39 PSI

===  Results of Testing ============

1)  Tank is about 1/4 full --  Ford says be at 1/2 to perform fuel system test -- but I can't see why make any difference.

2)  First key turn-on -- ONLY -- after sitting overnight (PSI- 30-32)
3)  2nd key turn-on -- ONLY -- (PSI 32-35)
4)  Start Engine.  PSI jumps to 39
5)  Turn off key, pressure drop to around 30-32 and stays there for 30 -40 seconds then gradually drop over next 2 minutes to between 20-25.
{Ford says after key turn-off pressur should remain minimum of 30 PSI "immediately" -- whatever length of time this is??.
6)  volume appears OK taking it out of the inlet rather than return line with vehicle running for 10 seconds.

=========  Question =========
1)  Pressure seems a little low (or am I being to precise)??
2)  If so, is this a function of high pressure pump on the rail or the
    pressure regulator on the TB?
3)  Would dirt in tank have an affect on pressure?

Fuel System Troubleshoot Questions

Reply #1 –
With the engine off my pressure drops, I never worried about it,as long as you got 39 running I don't see a problem. I'm not running TBI either, so It may matter.
Old Grey Cat to this.88 Cat, 5.0 HO, CW mounts, mass air, CI custom cam, afr165's, Tmoss worked cobra intake, BBK shorty's,off road h pipe, magnaflow ex. T-5,spec stage 2 clutch, 8.8 373 TC trac loc, che ajustables with bullits on the rear. 11" brakes up front. +

Fuel System Troubleshoot Questions

Reply #2 –
Kitz Kat:

Your response kind of my estimate on things but wanted to confirm with someone who's knowledgeable about Ford's TBI fuel system.

    With my filter clogging up [why Ford ever positioned the filter on the outlet side of the  high pressure pump is beyond me --logic says you'd want to catch dirt before it entered the pump to save the pump] every 10,000 miles, and getting an infrequent stall condition when the tank is low, IMHO appears to be more fuel rather than Ford's traditional TFI or stator problem.    Cleaning the tank can't hurt [see other posts], but if dirt has caused some clogging in the Pressure Regulator or injectors want to take care of that as well.

David