fuel pump question
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Joined: Dec 2003
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fuel pump question
I have a 98 mazda b4000 and have been having intermittent starting problems. I have had the truck towed to the dealer several times They have not been very helpfull. each time the only thing they have been able to tell me is what the problem isn't. I have replaced everything in the ignition system execpt the fuel pump. I haven't had any luck finding the schader valve to check the pressure, so I disconnected the fuel line at the imput side of the filter and turned on the ignition to start the pump. I was under the impression that the pump would pump until it reached the proper pressure then shut off. the pump ran for about 2 seconds then shut down. the amount of fuel that came out of the line wasn't much more that a couple of ounces. can anyone tell me if my thinking is correct that since the pump wasn't allowed to build up pressure that it should have continued to pump until I turned the ignition off. I believe I finally found the problem but wanted to verify my thought process before replacing the pump.
Posting Guru
Joined: Nov 2003
Posts: 1,221
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From: Homer, Alaska
It could be the fuel pump relay is causing the problem. Can you hear the pump run for about a second when you turn the key on? Locate the relay in the power distribution box and pull it out, clean the contacts,then replace it. Sometimes that will solve the problem.
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
The schrader valve is the small port located on the fuel supply manifold.
Standing in front of your truck with the hood open, on the top left hand side of the engine, just below the upper intake manifold, you will see the stainless steel (braided) flexible fuel supply line that connects to the fuel pulse damper (small metalic "mushroom" with vacuum line), which is itself attached to the fuel supply manfold. About an inch or two away from the damper is the schrader valve, mine has a blue cap on it.
It sounds to me like your pump is fine. Like Bob says, it only runs for a quick second or two when the key is turned to the "on" position. If and when the engine starts to crank over 250 rpm or so, then the pump begins running again.
Did you ever get a CEL? If so, were the codes pulled? If so, what were they? What did the dealer say?
Standing in front of your truck with the hood open, on the top left hand side of the engine, just below the upper intake manifold, you will see the stainless steel (braided) flexible fuel supply line that connects to the fuel pulse damper (small metalic "mushroom" with vacuum line), which is itself attached to the fuel supply manfold. About an inch or two away from the damper is the schrader valve, mine has a blue cap on it.
It sounds to me like your pump is fine. Like Bob says, it only runs for a quick second or two when the key is turned to the "on" position. If and when the engine starts to crank over 250 rpm or so, then the pump begins running again.
Did you ever get a CEL? If so, were the codes pulled? If so, what were they? What did the dealer say?
