Fuel Pump Issues

Stevo077 · January 2nd, 2012, 10:55 PM

Hey guys hope everyone is doing well, I haven't been on here for a couple months. My fuel pump is randomly shutting off at times, and for the life of me, I can't figure out why. First I replaced the relay, no luck, cleaned my IAC and threw on an extra mass air sensor I had laying around. Same problem, dropped my tank and replaced the pump but the problem still persists. The only thing I can think of would be something to do with the inertia switch possibly, or maybe something grounding out somewhere although all looked good. It only seems to do it while running or shortly after running, always starts right up after she's been sitting. Any ideas?

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ryanw · January 2nd, 2012, 10:59 PM

May be the computer

Stevo077 · January 2nd, 2012, 11:06 PM

I was thinking that too but figured it wasn't that likely for just the one thing to be effected you know. I don't know much about the computers, will they intermittently mess up one thing like that?

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ryanw · January 2nd, 2012, 11:30 PM

Im not sure, don't know enough about it. Maybe try listening to the relay and see if you hear it clicking on and off or check with a multi meter on the low volt computer Side of relay to see if your losing power

Stevo077 · January 3rd, 2012, 01:31 AM

I can hear it click, but it doesnt come from the relay, comes from under the hood, sounds like over by the MAF or that area. But it doesnt click when the fuel pump doesnt engage. I'll have to get my multimeter out and try and catch it doing it. It seems to only do it once i think its fixed lol. When im working on it, she always wants to start.

PONYMAN · January 3rd, 2012, 02:15 PM

Does it have a modulator ?
I have a fox & a new edge .
A few months back , we were going down the road & car just bogged down & stopped doing highway speed.
I had it towed in to the mechanic & he ran dianostic test & found out that my modulator was bad & had shorted out my fuel pump.
Before getting on the road that morning , we smelled a burning odor like a short while at a drive thru.
Best wishes hope you got that problem solved.

FastStang91Lx · January 3rd, 2012, 10:22 PM

I believe the modulator is only for returnless fuel systems. The fox's don't have that.

PONYMAN · January 4th, 2012, 09:42 AM

Originally Posted by FastStang91Lx

I believe the modulator is only for returnless fuel systems. The fox's don't have that.

thanks , I learn something new everyday here , love this board.

fogged306 · January 4th, 2012, 10:52 AM

Turn the ignition on and try wiggling your distributor and see if you get the same relay clicking sound under the hood.

If not then you need a test light and you need to check the fuel pump relay and see if it is getting power in and sending power out when this happens. If it still cuts out and the signal in to the relay, and the power connections are solid the whole time, then start moving down the line for the fuel pump circuit.

Stevo077 · January 4th, 2012, 11:23 PM

So since this weekend it hasn't done it, and I've put about 50 miles on it. The last thing I did was play with the inertia switch, wiggled it around and messed with the wires. I'm thinking it's going bad. I also noticed my horn wasn't working today. I'm not sure if that fuse had anything to do with it or not though.

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Stevo077 · January 9th, 2012, 12:44 AM

So I think this problem has something to do with my distributor. It seems like after I wiggle it around a little bit she starts right up. Any ideas? Popped the cap on it and there was some green build up on the tabs on the cap.

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ryanw · January 9th, 2012, 12:55 AM

I dont think the cap has any thing to do with your fuel pump not working, id keep looking

Stevo077 · January 9th, 2012, 03:26 AM

Won't the fuel pump not engage if it's not getting a spark?

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Stevo077 · January 19th, 2012, 09:54 AM

Weather hasn't been permitting to let me get out there with a multimeter yet, but I noticed that when the pump isn't priming, the check engine light also isn't on with the ignition on.

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mr_josh · January 19th, 2012, 10:03 AM

Time to start checking power to / at the ECM.

Stevo077 · January 19th, 2012, 10:23 AM

I have one of those sct chips I was thinking maybe it's going bad? Or if I was lucky could it be the EEC? hopefully though it's just a bad connection somewhere

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Stevo077 · February 1st, 2012, 03:32 PM

Figured it out last week, thought I'd let you guys know what it was. Turned out to be a faulty map sensor.

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ryanw · February 1st, 2012, 04:18 PM

Originally Posted by Stevo077

Figured it out last week, thought I'd let you guys know what it was. Turned out to be a faulty map sensor.

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Is that the box looking sensor in the middle of the fire wall ? How did you figure out that, it was the problem, and how did you test the sensor ?

Stevo077 · February 1st, 2012, 10:37 PM

Ya that would be it. I had my car started and was just trying to get it to stall out like it had been doing. When I tapped the sensor it would instantly stall out, and the CEL wouldn't come on til I messed with it some more.
First part store I went to said it was dealer only, and through ford it was $196. Luckily O'Reilys had an aftermarket one for $50 though.

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fogged306 · February 2nd, 2012, 01:52 AM

That doesn't sound right. The BAP sensor shouldn't have anything to do with your check engine light coming on with ignition or not. Should come on regardless. I think you may have some backfeeding issues going on here. It's possible that you have a bad computer ground and the computer was somehow getting it's ground through the BAP until that started to fail.. I could be wrong here, but I don't think you've 100% eliminated the issue. If it were me, I would pull the carpet back and check the ground to the computer. Should be the green bolt down in that area.

January 2nd, 2012, 10:55 PM	#1
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	Fuel Pump Issues Hey guys hope everyone is doing well, I haven't been on here for a couple months. My fuel pump is randomly shutting off at times, and for the life of me, I can't figure out why. First I replaced the relay, no luck, cleaned my IAC and threw on an extra mass air sensor I had laying around. Same problem, dropped my tank and replaced the pump but the problem still persists. The only thing I can think of would be something to do with the inertia switch possibly, or maybe something grounding out somewhere although all looked good. It only seems to do it while running or shortly after running, always starts right up after she's been sitting. Any ideas? Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

January 2nd, 2012, 10:59 PM	#2
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	May be the computer __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears

January 2nd, 2012, 11:06 PM	#3
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	I was thinking that too but figured it wasn't that likely for just the one thing to be effected you know. I don't know much about the computers, will they intermittently mess up one thing like that? Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

January 2nd, 2012, 11:30 PM	#4
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	Im not sure, don't know enough about it. Maybe try listening to the relay and see if you hear it clicking on and off or check with a multi meter on the low volt computer Side of relay to see if your losing power __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears

January 3rd, 2012, 01:31 AM	#5
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	I can hear it click, but it doesnt come from the relay, comes from under the hood, sounds like over by the MAF or that area. But it doesnt click when the fuel pump doesnt engage. I'll have to get my multimeter out and try and catch it doing it. It seems to only do it once i think its fixed lol. When im working on it, she always wants to start. __________________ 1990 Mustang GT

January 3rd, 2012, 02:15 PM	#6
PONYMAN Regular Join Date: Feb 2007 Location: Houston \ Flatonia Texas Posts: 215 iTrader: 0 reviews	Does it have a modulator ? I have a fox & a new edge . A few months back , we were going down the road & car just bogged down & stopped doing highway speed. I had it towed in to the mechanic & he ran dianostic test & found out that my modulator was bad & had shorted out my fuel pump. Before getting on the road that morning , we smelled a burning odor like a short while at a drive thru. Best wishes hope you got that problem solved. __________________ Have you driven a Ford lately ?

January 3rd, 2012, 10:22 PM	#7
FastStang91Lx I Post Entirely Way Too Much 1991 Mustang LX 5.0 Join Date: Jan 2010 Location: Minnesota Posts: 5,572 iTrader: 2 reviews	I believe the modulator is only for returnless fuel systems. The fox's don't have that. __________________ Point made in less than a few hours with minimal response. http://www.moddedmustangs.com/forums...ml#post4465184

January 4th, 2012, 10:52 AM	#9
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Turn the ignition on and try wiggling your distributor and see if you get the same relay clicking sound under the hood. If not then you need a test light and you need to check the fuel pump relay and see if it is getting power in and sending power out when this happens. If it still cuts out and the signal in to the relay, and the power connections are solid the whole time, then start moving down the line for the fuel pump circuit.

January 4th, 2012, 11:23 PM	#10
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	So since this weekend it hasn't done it, and I've put about 50 miles on it. The last thing I did was play with the inertia switch, wiggled it around and messed with the wires. I'm thinking it's going bad. I also noticed my horn wasn't working today. I'm not sure if that fuse had anything to do with it or not though. Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

January 9th, 2012, 12:44 AM	#11
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	So I think this problem has something to do with my distributor. It seems like after I wiggle it around a little bit she starts right up. Any ideas? Popped the cap on it and there was some green build up on the tabs on the cap. Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

January 9th, 2012, 12:55 AM	#12
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	I dont think the cap has any thing to do with your fuel pump not working, id keep looking __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears

January 9th, 2012, 03:26 AM	#13
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	Won't the fuel pump not engage if it's not getting a spark? Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

January 19th, 2012, 09:54 AM	#14
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	Weather hasn't been permitting to let me get out there with a multimeter yet, but I noticed that when the pump isn't priming, the check engine light also isn't on with the ignition on. Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

January 19th, 2012, 10:03 AM	#15
mr_josh Newbie Join Date: Aug 2009 Posts: 3 iTrader: 0 reviews	Time to start checking power to / at the ECM.

January 19th, 2012, 10:23 AM	#16
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	I have one of those sct chips I was thinking maybe it's going bad? Or if I was lucky could it be the EEC? hopefully though it's just a bad connection somewhere Sent from my SCH-M828C using AutoGuide.Com Free __________________ 1990 Mustang GT

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February 1st, 2012, 03:32 PM	#17
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	Figured it out last week, thought I'd let you guys know what it was. Turned out to be a faulty map sensor. Sent from my SCH-M828C using Tapatalk __________________ 1990 Mustang GT

February 1st, 2012, 10:37 PM	#19
Stevo077 Regular 1990 Mustang GT Join Date: Jun 2011 Location: NE Oklahoma Posts: 123 iTrader: 0 reviews	Ya that would be it. I had my car started and was just trying to get it to stall out like it had been doing. When I tapped the sensor it would instantly stall out, and the CEL wouldn't come on til I messed with it some more. First part store I went to said it was dealer only, and through ford it was $196. Luckily O'Reilys had an aftermarket one for $50 though. Sent from my SCH-M828C using Tapatalk __________________ 1990 Mustang GT

February 2nd, 2012, 01:52 AM	#20
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	That doesn't sound right. The BAP sensor shouldn't have anything to do with your check engine light coming on with ignition or not. Should come on regardless. I think you may have some backfeeding issues going on here. It's possible that you have a bad computer ground and the computer was somehow getting it's ground through the BAP until that started to fail.. I could be wrong here, but I don't think you've 100% eliminated the issue. If it were me, I would pull the carpet back and check the ground to the computer. Should be the green bolt down in that area.

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