Fuel pressure issues
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Mountain Pass
Joined: Nov 2004
Posts: 241
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From: Dayton Ohio
Fuel pressure issues
My 88 bronco is again wanting to start hard when cold so I tested the fuel pressure and it was 29 while running,I do not have a manual for it but the factory shop manual for my 89 crown vic says its supposed to be 30 to 45 while running so is that about the same for the trucks. Both pumps have been replaced along with the regulator and filter and relay so when the pressure is a little low what pump is the culprit,I have read that the ground the the fuel pumps is in the engine compartment and that is the only thing I have not checked so anyone know where its at on a 88. Both pumps seem to be a little more noisy then what they should be so I do need to check the ground.
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Mountain Pass
Joined: Nov 2004
Posts: 241
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From: Dayton Ohio
Did some looking and I think the ground in question is at a quick disconnect close to the battery and the wires were corroded up to the connector so it got removed,the insulation on the battery ground cable was split and it also was completely corroded on the inside so it got replaced. I still hard to start it twice when cold to keep it running so if the corrosion in the ground connection was the culprit on making the pump or pumps weak would the high pressure pump on the frame be the first to look into,if I do have to replace a pump I am thinking about going to the single pump system from a 90 and up or since I want to go to a 351 just go with a carb.
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Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
How fast does the pressure drop when you turn off the engine? If it drops real fast, the check valve in the pressure regulator may be bad. This will cause hard starts because the system needs to refill the lines to start.
You should have 38-42psi with the vacuum line off of the regulator and usually around 32psi with the vacuum line on.
You should have 38-42psi with the vacuum line off of the regulator and usually around 32psi with the vacuum line on.
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Mountain Pass
Joined: Nov 2004
Posts: 241
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From: Dayton Ohio
The fuel pressure does not rapidly drop,this truck has always surged when first fired up so I disconnected the regulator and it quit surging when first fired up so I am wondering if the high pressure pump is getting weak. Both pumps have been replaced but the in the tank pump went out and had to be replaced so I wondered if I weakened it when the rear pump went out.
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