losing prime??
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losing prime??
I've got a '90 F150 with 4.9l inline. That seems to be getting gas to rail but will not start. Even if primed it will only run until that gas is spent. Thinking about renting a pressure tester to check it at the rail. Have pulled and cleaned tank and replaced fuel lines going to rail. Any ideas??
Logistics Pro
Joined: Mar 2005
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From: Mexico, Missouri
You can short the fuel pump lead (Short end of connector) on the DLC plug to a good ground source and check to see if the in tank pump will stay running and if it is holding pressure on the fuel rail with a fuel pressure tester.
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Both pumps run. But don't know how well. Have pulled the line off the inlet of high pressure pump and low pressure (in tank) is pumping to that point. Have pulled the line by rail and getting gas to that point.
Post Fiend
Joined: Nov 2005
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From: Charles Town, W bygod Va
Verify high pressure pump is running, that fuel pressure gauge sounds like a really good idea. I like to verify a fuel delivery issue by spraying short shots of starting fluid or carb cleaner down the throttle body while cranking. It should start and you should be able to keep it running by giving it a little shot as the engine starts to stumble.
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Can hear the high pressure pump running but until I check the pressure I'm not sure it is putting out the pressure needed. I have sprayed some starting fluid in the throttle body but will only fire up until that fluid is used up. Doing this by myself so jumping in and out of the truck. Not as quick as I used to be.
Postmaster
Joined: Nov 2011
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From: SW Florida
Time to check fuel pressure. Don't know the exact specs for that engine but anything over 30 PSI should be enough for it to at least idle.
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Joined: Dec 2003
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From: Northern California
Can hear the high pressure pump running but until I check the pressure I'm not sure it is putting out the pressure needed. I have sprayed some starting fluid in the throttle body but will only fire up until that fluid is used up. Doing this by myself so jumping in and out of the truck. Not as quick as I used to be.
"Can hear the high pressure pump running"
Do the pump(s) run continiously when you turn the key to the "on" position and not the "start" position, or do they prime for about 1-2 seconds and then shut off ????
If the pumps run continiously in the "on" position, you've got a bad computer, EEC, PCM or whatever term you'd like to use.
Here's a link that might help.
A9x ECM's (and same years ECM's) Failures Due to Age
I'm not saying this is what you have going on, but, your truck does have the "symptoms" of a failing computer.
Bob
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Put a pressure tester on and doesn't read any pressure. The pump runs but apparently doesn't build up pressure. The good news is I found a gas leak. All the parts stores have told me that a 1990 only had one pump but a 1989 has two, is that true?
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