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Discussion Starter · #1 ·
I was cruising the Cobra out of boost and out of nowhere Fuel Pressure went to zero. Car has the stock returnless setup with twin GT pumps along with twin KB BAPs. I looked through the owners manual and checked the fuses and they were good. I had a spare set of GT pumps that I installed and still no fuel pressure. What am I missing to check here ? I will check even the most remedial things at this point. Any help would be greatly appreciated !

Thanks,
Mike
 

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If the FPDMs were deleted, there has to be a relay somewhere. Put a volt meter on the feed to it, and the trigger coil. Both should be 11-12.

Also, there is probably a direct fat pump supply wire with an inline aftermarket fuse.
 

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If you are still returnless like you said you can't delete the FPDMs unless there something to replace them like that zone5 Driver. You have to have something to vary the voltage to the pumps so fuel pressure can be maintained based on load.

I would check your FPDM or whatever you may have.
Also make sure you check the fuses on the Boost-A-Pumps themselves. They should be fused as well.
 

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The FPDM is in the trunk on the drivers side above the wheel well. You have to remove the cover to get to it.
 

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Something is getting lost in translation from your tuner. As speeddemon said, returnless requires a FPDM. Return systems can delete it/them.
 

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Discussion Starter · #9 ·
I may have misunderstood him because i looked and the are infact there.

I double checked all fuses and they are good

I put a brand new frps sensor on the rail and no fuel pressure

Installed a different set of working gt pumps and still nothing

When the key is cycled i can hear all the relays clicking but no audible groan from the fuel pumps.


I checked for codes via my sct and pulled the following

Po148
Po193
Po243
Po403
Po406

I did not clear the codes but there is no check engine light. The egr is deleted and is tuned out. I pulled a fuel line off and fuel comes out very slowly when the key is cycled. So for right now im lost lol
 

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Double check all your fused again. Did you check the fuse in the engine bay. Pretty sure there is one there.

After that first thing I would check is your voltage to the boost-a-pumps. You should be able to see the voltage at the fuse.

Then I would check the output wire on the boost-a-pump and make sure you are getting power there.

Then you need to check the power wires going into the FPDM and make sure they are getting power.
 

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I had a similar issue with my saleen a few years back. It was intermittent. Turned out to be the upgraded in line fuse directly off the battery. It had a very small crack. It would test ok cold but when it got hot would cut the power out. Replaced it and never had the problem again.
 

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I've found those big inline glass fuses to be constructed poorly. The one on my F150's amp power wire fell apart after about 8 years. I took it out of the fuse holder and I had one metal end loose, the glass tube loose, then the other meal end with the fuse portion sticking out. I took some solder tabs (flat square piece of solder) and put a couple in the end where the fuse came loose from. Heated it up until the solder melted then squeezed it back together with some pliers- pushing the loose end of the fuse into the liquid solder. It's worked fine for the last 5 years since I fixed it.
 

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Discussion Starter · #15 ·
I tested all the fuses in their holders and all tested good. I am going to replace all the fuses anyways because its a cheap and easy thing to do.

To be sure Im checking all the correct factory computer fuses, can anybody tell me exactly where all of the fuses are that make the cars fuel system work ? Or any fuses that are ultra cruicial in this situation ? I looked through the owners manual and checked what I thought pertained to the situation and they tested good with my test light.

Also, would the FRPS failure code trigger the fuel pumps to not turn on ? Like I said before, my SCT handheld does not have the ability to clear the codes ( its a 1st gen unit ) so Im going to unplug the battery for an hour and try that. After finding the codes, I did however re upload the tune and still a no start. I did not re check to see if it deleted the codes though.

What kind of voltage should I see at the input to the FPDM ?

What kind of voltage should I see at the output of the FPDM ?

What kind of Voltage should I see at the output of the BAPS ?

Im guessing the only way to check all of this is to do it right when the key is cycled so I'll need another set of hands.
 

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Discussion Starter · #16 ·
I've found those big inline glass fuses to be constructed poorly. The one on my F150's amp power wire fell apart after about 8 years. I took it out of the fuse holder and I had one metal end loose, the glass tube loose, then the other meal end with the fuse portion sticking out. I took some solder tabs (flat square piece of solder) and put a couple in the end where the fuse came loose from. Heated it up until the solder melted then squeezed it back together with some pliers- pushing the loose end of the fuse into the liquid solder. It's worked fine for the last 5 years since I fixed it.
I checked all around fairly good and I did not see a round fuse holder. The car seems to have all spade type fuses on it.

Just for the record, I did not install any of this stuff, it was on the car when I bought it. Because of this issue, I may end up ditching it all and going with a basic return style setup.
 

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If you have power to the pumps, and have tried another pair of pumps with no progress, it almost sounds like something as simple as a very clogged fuel filter. You said you have fuel dribbling out when you cycle the key? Definitely a fuel filter symptom. It's worth a shot...
 

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Ok sounds like you checked all the power from the front of the car to the FPDM 12V. Power to the Boost a pumps 12V how bout checking the power as close as you can get to the pump and see what the voltage is.
 
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