1993 5.0 EFI Fuel Issue/ Hard starting

Prince2e

Cadet
Joined
Aug 9, 2020
Messages
19
1993 5.0 302 EFI. Recently have had issues with it taking about 10 seconds to start after shutting the engine down for awhile. Went to check the fuel pressure at the rail. With the key on I got 5 PSI. With the engine cranked I got 30-31 PSI. When I shut the engine off, the gauge dropped 10 PSI in 10 minutes. Is this normal? Could this possibility be a fuel regulator going back or the check valve in the fuel pump?IMG_5876.jpeg
 

Prince2e

Cadet
Joined
Aug 9, 2020
Messages
19
1993 5.0 302 EFI. Recently have had issues with it taking about 10 seconds to start after shutting the engine down for awhile. Went to check the fuel pressure at the rail. With the key on I got 5 PSI. With the engine cranked I got 30-31 PSI. When I shut the engine off, the gauge dropped 10 PSI in 10 minutes. Is this normal? Could this possibility be a fuel regulator going back or the check valve in the fuel pump? IMG_5876.jpeg
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,561
Looking at what I have for a wiring diagram, the FP is energized by the ECM. The ECM applies a ground to one side of the relay coil. The issue is I don't know if it turns ON like newer Merc/VP or if only during cranking.

Measure power on both sides of the coil (pins 85 and 86). Do this when power is first turned ON and while cranking. When the FP is OFF you should see 12V on both sides of the coil. When the FP is turned ON you will only see 12V on one side of the coil
 
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