1991 Ford Bronco



August, 27, 2009 AT 12:49 AM

Engine Mechanical problem
1991 Ford Bronco V8 Four Wheel Drive Automatic 143000 miles

I've been hacking away at this issue for about 2 weeks now, and I'll tell you what I have done so far to eliminate possibilites.

1) Changed all my sparks, rotor, and cap.

2) Cleaned battery cables

3) Overnight fuel line pressure test (which stayed in proper PSI range) - maybe I need to do more extensive fuel pressure tests?

4) Replaced fuel filter

I ran a test recommended by a friend. Turned the key to on position, let the pump prime, then off. They did this again, and then cranked up the engine - it appeared to start normal after this test on a cold start.

So the first assumption was a fuel pressure issue - but it's a bit hard for me to believe the fuel pump is bad if it's priming and getting power OK.


a) Engine starts up 2-3 rotations when engine is warmed up (like normal).

b) I've been told this is most likely a fuel pump issue, but I did not want to jump the gun and spend all of that dough until I felt like the issue was really nailed.

I would really like to solve this issue! So thanks much in advance for any tips or advice to consider.

4 Answers



August, 27, 2009 AT 1:40 AM

The only way to rule out the fuel pump is you have to check the fuel pressure with a fuel pressure gauge designed for your fuel system.

EFI system don't like low fuel pressure-could be a leaking fuel pressure regulator or injectors.




August, 27, 2009 AT 9:29 AM

Ok, thanks for the note.

Do you know of or can you provide a diagnosis checklist of some kind for running all these tests?



August, 27, 2009 AT 10:35 AM

Get a fuel pressure tester hook it up on the fuel pressure test port/schrader vale turn key to run and read off the pressure use specs above and then comeback with the readings

****3) Overnight fuel line pressure test (which stayed in proper PSI range) - maybe I need to do more extensive fuel pressure tests? ****

Do you hear the fuel pump come on when you turn key to run? If so do the fuel pressure test if not investigate and test the fuel pump relay and pump fuse, inertia switch.



August, 27, 2009 AT 11:19 PM


Here are my readings and answers: 1) Pump is priming OK (when ignition is turned to ON position).

2) Connected pressure to shrader valve and results are as follows: -- Ignition in ON position: 35 PSI (pump primes OK)

-- Engine running: 32 PSI

-- Turn off engine: 35 PSI (stays steady at this)

I noticed I might have not had my fuel filter clamped very well when I checked it today, and so secured it properly.

I am going to run the tests in the AM again just to see if the fastening of the fuel filter might have been the issue all along.

Remember the only issue is when I start up the engine on a cold start (after sitting overnight), it needs to crank 8-10 times before the engine fires up. Maybe the fuel filter was hanging in such a way that the fuel was dropping backward and holding in the filter instead of staying in line. Anyhow will check in the AM to see if the 8-10 cranks is still happening.

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