Bad Fuel Pump?
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Joined: Feb 2003
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Bad Fuel Pump?
Hi all, My '91 Bronco starts hard after it's sat for more than an hour or so. Takes like 4-5 cranks to get it to run. It has the 4.9L EFI. I used my Hanye's manual and a fuel gage to run the tests and here are my results.
Engine off key on: 26 psi at the fuel rail
Engine on FP regulator connected: 42 psi
Engine on FP regulator unhooked: 48 psi
Static pressure test: passed
I definately have and underpressure problem and yes...I already replaced the fuel filter and checked for kinks in all the fuel lines. I have a complete used fuel delivery module from a '96 and was wondering if I could swap the pump out of it into my '91 FDM. Has anyone done this swap? Do all the late model bronco's use the same pump? It says 125 LPH (liters per hour?) and 310 KPA on it.
Not looking forward to dropping that tank.
Engine off key on: 26 psi at the fuel rail
Engine on FP regulator connected: 42 psi
Engine on FP regulator unhooked: 48 psi
Static pressure test: passed
I definately have and underpressure problem and yes...I already replaced the fuel filter and checked for kinks in all the fuel lines. I have a complete used fuel delivery module from a '96 and was wondering if I could swap the pump out of it into my '91 FDM. Has anyone done this swap? Do all the late model bronco's use the same pump? It says 125 LPH (liters per hour?) and 310 KPA on it.
Not looking forward to dropping that tank.
New User
Joined: Jul 2003
Posts: 8
Likes: 0
From: Oklahoma City
Bad Fuel Pump?
If you cycle your key on and off several times to build up fuel pressure in the rail before you engage the starter does that make it start any quicker? If the answer is no, then I would look at replacing the fuel pressure regulator, or having the injectors proffesionally cleaned. If the answer is yes, then there might be an anti-drain back valve on the fuel pump assembly that is leaking.
I've had the tank out of my Bronco several times. If you use an Air wrench to remove the skid plate mounting nuts and bolts it's not too bad...if the tank is completely empty that is. I'd also spend $5.00 at a high pressure wash before I started and make sure you have somebody available to hold the tank while you get the first couple of Nuts started when you put it back in.
Good luck.
I've had the tank out of my Bronco several times. If you use an Air wrench to remove the skid plate mounting nuts and bolts it's not too bad...if the tank is completely empty that is. I'd also spend $5.00 at a high pressure wash before I started and make sure you have somebody available to hold the tank while you get the first couple of Nuts started when you put it back in.
Good luck.
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