1989 Bronco II, 2.9L no fuel pressure on rail. When I turn on the ignition, I can hear the pump startup and then after a few seconds turn off. When removing the fuel line to the Rail there is fuel coming out of the line, yet there is no pressure at the Shrader valve. The engine runs fine when we inject fuel into the Air Intake. Have checked the inertia switch, removed the wires and reinstalled, reset the red button.
Any ideas? how much pressure should we have at the fuel line as it enters the rail?
Thanks
Dick

 

With key on/engine off the fuel pressure regulator drops the pressure at the schrader valve to 40 PSI. So on the fuel pump side off the FPR you should see something above 40 PSI

 

Thanks for the response, with key on engine off, the pump comes on for about 3 seconds and then shuts off. We have checked the supply line at the tank side of the fuel filter, and before the FPR. There is no pressure, nada. If we turn the key on then off then on etc quickly, then we are able to keep the pump running often enuf to get some fuel through the line but not enuf to pressurize the rail. We have bypassed the inertial switch and get the same results.

BTW, this is a new pump in the tank which the owner just installed and a complete overhauled engine. Again, the engine runs great using a rag soaked in fuel next to the air intake.

Dick

 

Well the way this it's supposed to work is the low pressure in tank pump sends fuel to the high pressure frame mount pump. Sounds like that new pump might be defective or possibly a kink in the line somewhere?? I have heard that some aftermarket fuel pumps are garbage & that it's best to go with OEM. One other thought, does this have a canister style black fuel filter housing? If it does it is just excess baggage & should'nt have a filter in it. I have heard of some guys that have somehow found & installed a filter in it. If you are checking pressure between that housing & the pump dont mess with it because O rings to seal it are hard to find. OTOH if there is a filter in there it might be clogged.

 

OOPS, you did say that this is an 89 which means that you only have the in tank fuel pump.

 

There is a canister attached to the frame, however, when we disconnected the fuel line between the tank and the canister we still did not have bunches of fuel with the key on engine off. How long should the pump run?, until pressure regulator turns it off or is there a built in timer inside the pump? Seems to me that if you energize the pump and do not connect the fuel line to anything, the pump should run until the power is turned off.

 

Running for 3 seconds is normal and you should have instant fuel pressure, once the engine is running the pump runs non stop. I'm no expert on this stuff, but it sounds like you need to drop the tank & check out that fuel pump.

 

Thanks, I agree, on researching similar problems here I read one response which stated if there is no pressure, check for kinks in the line, clogged filter, clogged fuel pump screen and lastly if all of those are ok, proper pump operation.

I also understand that if the injectors sat around for a extended period that they will be frozen. In this case, they have been sitting for at least that period of time. Is there a way to check the injectors to see if they will fire?

Dick

 

Since it has a new pump my guess would be a cloged pump screen, maybe theres rust or???in the tank. Since it runs when you provide the fuel at the throttle body, I would'nt worry about the injectors.

 

OOPS again when you sqirt fuel into the throttle body it is sucked directly into the cylinders thru the intake valves. But until you get pressure to the fuel rail I would'nt worry about the injectors.
One other thing that I just found out is if there is a break anywhere in the return line from the fuel pressure regulator to the tank it wont pump, you will get zero fuel pressure. TO check for this you can BRIEFLY pinch off the return line under the hood & if you get pressure at the schrader valve there is a hole in the return line somewhere. I say briefly beacause it puts a heavy load on the fuel pump.
By the time you get this thing running we are both going to know a lot more about how our fuel systems work.

 

Thanks again, will look at these ideas in the ayem. Kinda dark here.

Dick

 

As a diagnostic aid, one of the leads of the self-test connector (same connector used for pulling codes) can be used to control the fuel pump. Might simplify diagnostics because then you could turn the key on, ground this connector, and the pump will run and you can see if the fuel pressure in the rail comes up.

 

Thought I would relate the solution to the lack of rail fuel pressure. A little background, my next door neighbor started overhauling the 2.9L from his 89 BII about a year ago and installed it in the vehicle about a week ago. He is the kind of guy that won't ask for help until he is totally exasperated. I was brought into this yesterday and asked for help here because I really am not a mechanic but I can read reasonably well and enjoy troubleshooting problems.

As we know, the fuel pump was new and there were no restrictions in the fuel lines going to and from the FPR. Since I could not get fuel through the canister, I suggested that we pull the tank and check the pump strainer. When we did this there was no evidence of any trash, he did tell me that the tank had been purged, I just had to see for myself. Then looking at the pump itself there was a definite difference between the OEM and the new pump so I suggested that he check the part number and low and behold it was a low pressure pump instead of a high pressure. After replacing the pump and putting it all together we were still unable to get pressure at the rail even though we had plenty of fuel at the inlet, it was not going into the rail. We removed the Shrader valve and using high pressure air we blew out the rail.
Large pieces of dirt from dirt daubber nests came out of the inlet of the rail. We attached the fuel line, turned on the key and bingo, runs great.

Next time you hear someone with this issue ask them if they live in Florida where dirt daubbers like to make nests in anything that has a small round hole.

All in all quite a experience. I would like to thank you for your help, keep up the good work.

Dick

 

And thank you for the very interesting update. No wonder this was such a pain to figure out, glad to hear it's running good now. I did a search on dirt daubers & I see that other than where they sometimes choose to build there nest they are a very good critter to have around, since one of there favorite meals are black widows. It's a good thing that the guy still had the old pump to compare to otherwise this could have really gotten into long division. Congrats on the fix.