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Unthought of Solution


freedom5

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Recently when my 2.9 wouldn't start I thought the fuel pump had failed. During trouble shooting I discovered the fuel pump relay (the original '87) was full of corrosion. I cleaned all of the contacts and replaced the relay and found that it also solved some other problems often posted on the forum, ie hesitation on rapid acceleration or bogging down. Now my 2.9 is running like new. I can only guess that there was enough voltage drop to the fuel pump because of the corrosion to keep it from providing enough fuel called for by the computer during these situations.

I constantly see posts of the situation described above but no mention of checking the FP Relay. Just wanted to pass this on. The relay is a cheap item and could be a simple solution.

Freedom5
 


RonD

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Yes, Fuel Pump relay and socket can get corrosion as they get older.

Once engine RPMs are above 500 the computer closes that relay and it won't open again until key is shut off or RPMs are below 500(stall).
So fuel pump is always on when engine is running, computer doesn't have a pressure sensor.
But relay is held closed by the 13-14volts(alternator) passing thru it's coil, as you said if corrosion lowers voltage at the relay then relay could open and close at random times, i.e. lower RPMs because alternator voltage can drop a bit, so cause low pressure symptoms as you described.
 
ranger_redneck

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so where is this relay located?
 

RonD

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There are 3 relays near each other:
EEC Relay, powers computer(EEC), fuel injectors, fuel pump relay and spark system, Brown base
Fuel Pump relay, Green Base
WOT(wide open throttle) relay, Black base
Usually on passenger side wheel well

However when the added the engine compartment fuse box they were put under it

Around 1990-2 they are IN the fuse box
 
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