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Ask Derek Werner Your Own Question
Derek Werner
Derek Werner, ASE Certified Technician
Category: Ford
Satisfied Customers: 137
Experience:  ASE Master Technician, L1 Advanced level specialist
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98 explorer starts after 2-4 seconds but no prime time on

Customer Question

98 explorer starts after 2-4 seconds but no prime time on fuel pump.
Submitted: 1 year ago.
Category: Ford
Expert:  Derek Werner replied 1 year ago.

Hello and welcome!

What is the 8th letter in the VIN? This will tell me what engine the vehicle has.

Have you checked fuel pressure with a gauge? This is the first test that should be done. There is a fuel pressure test port on the fuel rail borrow a pressure gauge from a auto parts store to test. Fuel pressure spec is, key on engine off 30-45psi. Key on engine running, 27-42psi.

Customer: replied 1 year ago.
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Customer: replied 1 year ago.
I would like to know how the fuel prime 2 seconds is accomplished. I can live with the present situation but not happy with it. I believe the fuel pressure is OK because it starts and runs good but there is no prime. I must be getting good oil pressure because it starts after cranking for just a second or two, but not immediately like it always has.
Expert:  Derek Werner replied 1 year ago.

Oh ok i understand, first i thought you were saying the engine only ran for a few seconds. What you are describing is a long crank before the vehicle fires up.

The Fuel pump prime is controlled by the pcm. The PCM will ground the fuel pump relay for a few seconds Key on to pressurize the fuel system. There is a check valve located inside the fuel pump, this is to keep fuel inside the fuel lines and rail for a normal start up. When this check valve fails fuel pressure bleeds off back to the fuel tank causing a long crank time. If the engine runs then the prime is working normally as this is control on the same circuit that turns the pump on.

A fuel pressure gauge is normally used to check for a failed fuel pump check valve. After the engine is ran and shut off fuel pressure should hold for up to 30 minutes. Another way to confirm the check valve is at fault is to cycle the key off and on several times before starting the vehicle. After doing this and the engine starts and runs good then the fuel pump should be replaced. The check valve can not be replaced separately from the pump.

Customer: replied 1 year ago.
Thanks Will:
Tried your suggestion cycling the key and there was no difference in the cranking/start problem. I could hear a click in the back but I think it was in the unit for the alarm system. (PAT or PAS?) Anyway, this leads me to believe the problem is not the fuel pump but that old gremlin "ground remover". I'll check for bad grounds and see if that takes care of it before I get into the pump. Appreciate the help and info.
Bob
Expert:  Derek Werner replied 1 year ago.

Hi Bob,

The PATS passive anti theft system will cause a no crank no start if the system had a error, and the theft light would flash rapidly.

I have not heard of a Ground remover before? Unless you are referring to a poor ground connection due to high resistance, to check for this a voltage drop test will need to be performed.

Hard start can also be caused by a excessive rich or lean running engine, with a check engine light on.

Leaking fuel injectors, or leaking intake manifold gaskets.

After the engine has ran does this problem occur all the time or after the vehicle sits.