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Discussion Starter #1
I replaced my fuel pump. I can hear the new one turn on. But only for about 3/4 of a second. Then it shuts off. I had replaced the filter before I figured that the pump was bad and the pressure was pretty high. Now when I remove the filter. There isn't any pressure. Why would the pump only turn on for less than a second if pressure is not at all present.
 

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Discussion Starter #5
Relay test is good. The pump kicks on for .75 seconds when 12v is applied. While cranking the fuel pump is not heard, immediately after cranking stops, fuel pump can be heard for another .75 seconds.

applied 12v directly to pump to keep it constantly running. Still no joy.

Ran compressed air through line from filter back. No obstructions present.

could this be a bad pump right out of the box???? Sure but it doesn't seem that way with the pump on and being heard.
 

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Discussion Starter #6
It was a bad pump right out of the box. One the bright side I replaced or treated the following and it runs better than it ever had.

Ignition coil
Tps
Cap rotor and plugs
Cleaned iac
Cleaned throttle body
Fuel pump relay
Harness for fuel pump was broken so that was replaced too

no more hunting idle. No hesitation. Hopefully gas mileage will double. I was only at 5-7. I will update on mileage as soon as possible. I drive less than 200 miles a month so it may take a while.
 

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Discussion Starter #7
Ok so now another bad fuel pump right out of the box? Same thing... can hear it turn on with ignition but it shuts off again. Either these are garbage pumps or something is killing them.
 

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Discussion Starter #8
Am I making improper electrical splices. My low voltage background tells me that having + and - 12vDC both exposed to the same body of liquid is not a good thing. However the original pump that went out was connected the same way and there aren't any weather proof fittings included. Just the generic butt splice things. So what gives. I can't imagine why fuel pumps keep going out. The local autozone has just sold me the last one of this particular brand. They aren't going to carry anymore. They have replaced them with the Delphi brand. Any comments are most appreciated!
 

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What pump are you talking about? The lift pump in the fuel tank or the HP pump on the frame rail? Did you follow Seattle's link? If memory serves the EEC actually pulls the relay coil to ground, 12v should always be present, and the pump should run for 3 seconds when the ignition is turned on, not .75 seconds...

Here are my thoughts though even though we don't have a lot to go on.

A) If the lift pump is bad, then the HP will almost never be able to build adequate pressure.

B) How do you know there is no pressure? By breaking into lines that should be charged? Do yourself a favor and go spend the $20 on a FP gauge, hook it to the schrader valve on the fuel rail and get some real information.

C) Entirely possible that the EEC is not firing injectors. If when you get the FP gauge and you do find that you have fuel pressure, then you need to get a tool called a "noid light" they sell a set at HF for pretty cheap, and I'm pretty sure you can rent one from Autozone as well.

D) If it is actually the in tank pump that you have been replacing, then you might want to devote some attention to the HP frame rail pump.

I didn't go through your whole other thread, just this one, so you may have already checked some of this stuff.

Good Luck,
Jason
 

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What pump are you talking about? The lift pump in the fuel tank or the HP pump on the frame rail? Did you follow Seattle's link? If memory serves the EEC actually pulls the relay coil to ground, 12v should always be present, and the pump should run for 3 seconds when the ignition is turned on, not .75 seconds...

Here are my thoughts though even though we don't have a lot to go on.

A) If the lift pump is bad, then the HP will almost never be able to build adequate pressure.

B) How do you know there is no pressure? By breaking into lines that should be charged? Do yourself a favor and go spend the $20 on a FP gauge, hook it to the schrader valve on the fuel rail and get some real information.

C) Entirely possible that the EEC is not firing injectors. If when you get the FP gauge and you do find that you have fuel pressure, then you need to get a tool called a "noid light" they sell a set at HF for pretty cheap, and I'm pretty sure you can rent one from Autozone as well.

D) If it is actually the in tank pump that you have been replacing, then you might want to devote some attention to the HP frame rail pump.

I didn't go through your whole other thread, just this one, so you may have already checked some of this stuff.

Good Luck,
Jason
90 model year only has one fuel pump internally to the tank. It is a High pressure pump all bundled into one. The frame mounted high pressure pumps with low pressure in tank pumps were dropped in 89 or 90.
 

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Am I making improper electrical splices. My low voltage background tells me that having + and - 12vDC both exposed to the same body of liquid is not a good thing. However the original pump that went out was connected the same way and there aren't any weather proof fittings included. Just the generic butt splice things. So what gives. I can't imagine why fuel pumps keep going out. The local autozone has just sold me the last one of this particular brand. They aren't going to carry anymore. They have replaced them with the Delphi brand. Any comments are most appreciated!
What brand pump are you installing?

If your wiring is bad between the pump and the relay it may start the pump but not be able to supply enough current to keep the pump going.
 

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Discussion Starter #12
Airtex is the brand. I will check voltage tomorrow. I'm almost positive voltage is good. I gave the first pump 12vdc from another vehicle, ground came from mine. This basically just bypassed the relay and made the pump constant on. The pump was on but no pressure. Once again though, local autozone stopped carrying this brand in order to replace it with delphi brand.
 

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Discussion Starter #13
I think it's in tank pump because when I replaced it the first time my truck started right up. Ran fine for a day then nothing. Same thing with this second pump. I'll get the pressure Gauge and check into.
 

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Discussion Starter #14
Also, I thought I remembered someone saying 89 was the last year for the dual pump setup.
 

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weak wiring to the pump will kill them, they need a full 13v+ for longevity

If its killing pumps every other day then you have trash in the tank

yank the tank and flush it out with some acetone

also, verify the regulator isnt leaking
 

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Discussion Starter #16
weak wiring to the pump will kill them, they need a full 13v+ for longevity

If its killing pumps every other day then you have trash in the tank

yank the tank and flush it out with some acetone

also, verify the regulator isnt leaking

It's entirely possible there is something in the tank. The first replacement I had to drop the tank. There was so much crud under and around the snap ring some of it may have gotten in there. I'll buy a filter sock and strain it. The ones you can get from fish stores are the best. I use them for all sorts of filtering. Problem is I filled my tank on the last pump I installed. So, that means I have a lot of siphoning to do. All of this is difficult in a one car apartment garage lacking electricity.

Regarding voltage, I don't believe that to be the case. I ran 12vDC from a 2014 dodge cv. Grounded to the bronco then applied + directly to the pump. The pump was on constant. Still no joy. I haven't measured amperage yet (because it sucks when you get zapped) but with flickering of lights at 45+ mph and gauge reading 16-18 volts while idling, I would doubt it's a voltage lacking issue. Every truck I've seen with flickering lights has a H.O. alternator that isn't being utilized fully. 12vdc electronics usually have a safe operating range of 10-18 vDC to allow for variances in their power supplies.
 

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Airtex pumps are indeed junk, I used to work in the industry and they were always being returned. Delphi is a much better brand, they even supply oem pumps.

As far as wiring goes, gasoline does not conduct electricity that's why both terminals are and can be exposed.

Id say give the delphi pump a shot and see if you keep having the same issue. Make sure you put a new sock on the pump.

When youre at the part store maybe rent the fuel pressure tester. Seems odd that it wont run with direct power to the pump unless its just not pumping.
 

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Discussion Starter #18
On both replacements it started right up that day. Both times I came out 2 days later and wouldn't start. Truck is in a garage so I know there hasn't been any tampering. Gonna blow air through the return line and see if that helps.maybe something got in that line and is being returned inside the pump only to tear up the new pumps. Glad to hear airtex is junk. Hopefully that's the only issue.
 

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90 model year only has one fuel pump internally to the tank. It is a High pressure pump all bundled into one. The frame mounted high pressure pumps with low pressure in tank pumps were dropped in 89 or 90.
Sorry, I forgot about that. My old '89 had both. Thought the '90 was the same. Anyhow, carry on!

Later,
Jason
 
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