fuel pump

[belkin]

How can you tell when a fuel pump goes bad?Does the engine shut down or over time it's harder to start and fineally won't start?

[edgray]

after installing a new filter, a pressure test at the fuel rail on the engine while driving down the road (under load) is a recommended method. I think. Ed

[DriVer]

Quote:

Originally Posted by belkin How can you tell when a fuel pump goes bad? Does the engine shut down or over time it's harder to start and finally won't start?

belkin, During the course of my most recent fuel pump failure - the short answer to your question is "Yes"; The engine (may) shut down and over time it gets harder to start and finally won't start at all. Needed to get towed to service center from about 1 mi away from my house. (Insurance covered the tow)

What ED suggested in his post is an accurate method of diagnosis. A fuel pressure gauge on the rail will show you what's happening. My pressure went to "0" when it finally gave up the ghost.

[belkin]

Thanks for your help! I recently came back from a day trip ,shut the engine down for about fifteen minutes when i tried to restart it had to crank acouple of times were normally it would instant start/

[M&EM]

Quote:

Originally Posted by belkin Thanks for your help! I recently came back from a day trip ,shut the engine down for about fifteen minutes when i tried to restart it had to crank acouple of times were normally it would instant start/

I experience similar restart difficulty for the past year and have found it to be related to leakage at the fuel pump outlet (probably a check valve). As Ed Gray mentioned, Fuel rail pressure tests continue to show proper fuel pressures while running and on the road under load. Pressures should be around 52-55 at idle with vacuum line connected. 60-65 I think, with vacuum line disconnected. I thought my rail regulator was not holding pressure but subsequent test showed it to hold 52 psi indefinetly with external air applied to fuel line past fuel filter. At 70,000 miles I am considering a new pump anyway. Until then I will monitor pressure periodically for unusual changes.

Marty

[pkmesser]

Maybe this could be a question for a poll for the Workhorse forum. At what milage/age have fuel pumps failed?

Not the same vehicle, but:
I towed my son's F150 to my house just yesterday, now trying to decide which is easier/harder, dropping the tank, or pulling the bed off.

[pkmesser]

Quote:

Originally Posted by M&EM I experience similar restart difficulty for the past year and have found it to be related to leakage at the fuel pump outlet (probably a check valve). As Ed Gray mentioned, Fuel rail pressure tests continue to show proper fuel pressures while running and on the road under load. Pressures should be around 52-55 at idle with vacuum line connected. 60-65 I think, with vacuum line disconnected. I thought my rail regulator was not holding pressure but subsequent test showed it to hold 52 psi indefinetly with external air applied to fuel line past fuel filter. At 70,000 miles I am considering a new pump anyway. Until then I will monitor pressure periodically for unusual changes. Marty

With the pressure bleedoff, have you tried turning the key to run position for a few seconds before cranking? Not sure, but it might work.

[DriVer]

Quote:

Originally Posted by pkmesser With the pressure bleedoff, have you tried turning the key to run position for a few seconds before cranking? Not sure, but it might work.

As soon as a driver turns the key on the pump pressurizes the rail.

[ga traveler]

Quote:

Originally Posted by pkmesser With the pressure bleedoff, have you tried turning the key to run position for a few seconds before cranking? Not sure, but it might work.

Almost all fuel injected gas engines run the fuel pump for 2 seconds when the switch is turned on. If you want to prime the engine, turn the switch on for 2 seconds. turn off. turn back on 2 seconds. then off again.
if you ever run out of gas, this is how you reprime the engine. Of course it will take many times.

[M&EM]

Quote:

Originally Posted by pkmesser With the pressure bleedoff, have you tried turning the key to run position for a few seconds before cranking? Not sure, but it might work.

.
Yes, this has become my normal start up procedure. I have observed the pressure fall off to be quite rapid so at least two primes in rapid succession seems to work consistently with the start position used immediately after the second prime. I am able to hear the pump prime sequence start and end. I have taken apart some replaced pumps from my other vehicles and found each to have some form of check valve at the pumps out let as well as rubber hose connections that can offer leakage opportunities.

The symptoms I describe here could also be explained by the possibility that the short rubber hose connecting the pumps output to the metal fuel piping inside the tank is leaking. Either cause requires tank removal for repair! An external check valve may also be a solution

Marty

[belkin]

wow there is alot of knowledge out here,you were talking about turning the key a couple of times to prime before you start,well I was doing that for awhile last year when all of a sudden my whole dash panel everything went dead,blank,no responce from the ignition switch.Got that fixed but still have the problem I guess with the fuel pump,or regulator I have to check that.Thanks for the help!

[pkmesser]

Quote:

Originally Posted by DriVer As soon as a driver turns the key on the pump pressurizes the rail.

But if all pressure has bled off, this will not be instantanious. As pointed out by others in later posts, it seems to work to a degree. If having the issue, this avoids spinning engine with starter until fuel pump pressureizes fuel rail.

[DriVer]

Quote:

Originally Posted by pkmesser But if all pressure has bled off, this will not be instantaneous. As pointed out by others in later posts, it seems to work to a degree. If having the issue, this avoids spinning engine with starter until fuel pump pressurizes fuel rail.

A 60 psi surge from a device like a fuel pump will pressurize the fuel system and rail practically instantly. The fuel line is small in diameter and as such is not all that difficult to pressurize.

You can spin the starter over all day long but if the pump isn't putting out any pressure the vehicle will not start .... been there and done that. If you have a bad pump that might come up, the starter will spin over the engine and it might start .... been there too.

If my vehicle sits for a month, I can go out on the pad and start the engine on a the first attempt using a 2 second crank time or less. My pressure as far as I know does not bleed off. Never a problem starting my engine when the fuel pump is known to be good. Even if it does bleed off, I have not had an long crank time to start the engine after an extended period of disuse.

I am not sure if instantaneous is required but I can guarantee this, you are not going to hold your thumb on the out put side of the fuel filter once that pump cranks up. 60 psi is a lot of pressure.

Bottom line is the fuel system is either working or not. If it's hard to start its broke.