FUEL pump diagnosis question

[BMWM3]

Almost a year ago my buddy bought upgraded fuel system from SHpermformance here on the forums. we bought the fuel system to handle over 600hp, twin pumps return style.

For awhile we have been feeling like the car has been down on power. Searching issues on the forums, we see some people say that don't like the twin pump set up b/c one pump could go out and they would not even know and get into boost and car would go lean. Is this possible, is there a fail safe to prevent this; if there isn't one can a solution be performed to prevent that scenario.

Well anyhow last night i was driving the car and all of sudden the car cut off on me shifting from 2nd doing about 30mph. I was a stop sign, when i gave it gas it started pooting like sometimes when you are in 1st and you don't give it enough gas and it dies on you. I know the fuel system pumps are loud and very noticeable and I do not here the fuel pumps cut on. We pulled the fuel system out to see if anything was loose, and we found nothing. My friend thinks that maybe both pumps finally went out and the reason why i noticed a lack of power recently before was b/c the 1st pump went out a long time ago and now the 2nd pump went out. Luckily I have never had the car pass 3500 for over 4 months and could be the reason why it has never went really lean and blown. He said he will come back with a volt meter to test the pumps and see if it's getting power. Is there any thing else i'm missing that i need to check for.

The steps we have performed so far.
--checked fuel pump amp fuse directly to battery
-- switched relay 7018 out with another relay for fuel relay
-- checked fuel pump fuse (i think its either band 41 or 43)
-- pulled fuel pump do not see any loose wires
------problem fuel pumps are not pumping---

What else do i need to look for?

 

[BruceH]

You aren't going to have much to go on until fuel pump voltage is checked.

 

[JeremyH]

If its got my wire upgrade then both pumps are run on the same fuse and wire so if a pump shorts or fails and pops the fuse both pumps go out. Other than that no other way to really do it. You can wire up indicator lights etc for each pump. But these just run off voltage. If a pump has failed voltage will still get to the pump, but that doesn't mean its working and still moving fuel.

Drop the hat in a bucket with some gas. Apply 12 volts from the car battery to the pump leads momentarily to see if you get flow coming out. That will let you know if its a pump issue. If the pumps still work I can walk you threw checking for voltage at key on at different places.

Is there a fuel pressure gauge or can he datalog fuel pressure? That's another easy way to see whats going on with the fuel system.

To recap, since the hat is out make sure the pumps work first. Then move on to things like stepping through voltage checks, relay, inertia switch and fpdm/fpdm connection.

 

[sprchrgd s197]

Ok, I'm waiting on my buddy to get back so we can check everything. But like BMWM3 said I pulled the pumps this morning and it looked fine. But I have been feeling like it was down on power but couldn't figure out what it was. But I'm no mechanic so I'll have to pay to get this figured out. Just wondering if one of those pumps went out some time ago. But my boy will check to see if it's getting power later.

 

[TexasBlownV8]

I diagnosed my fuel pump issues by noticing what the fuel pressure was doing; it was too low, and voltages where right.
If you're not getting power, the car wont even start, you'll have no pressure at all. But if there is an intermittent voltage issue, that could be a little more tricky to find.

 

[sprchrgd s197]

Didn't get a chance to check it yesterday. Somebody I know wanted to party instead. LOL! So we'll try today to check for power going to the pumps. I'll keep you guys posted because I'm sure I'll need help trying to figure it out. BTW Happy Fathers Day to everyone.

 

[BMWM3]

It ended being a fuse we checeked 4 times FOR CERTAIN....

I checked the fuse twice, Supercharg197 came behind me pulled the fuse checked it behind me. Then he went to check to the boost a pump, and he checked that fuse it was good. He woke up decided to recheck all the fuses again and then he noticed it was a bad 30amp fuse. ....

 

[TexasBlownV8]

But, why did it blow?

 

[JeremyH]

Which fuse was it, and exactly now you need to find out why it went.

 

[Fullboogie]

I take it you visually checked the fuse instead of running a continuity test?

 

[BMWM3]

i don't know why it blew... All the wires looked good, all connections are tight. nothing loose... have no clue why it blew.

 

[JeremyH]

I would bench test the pumps Like I mentioned earlier, if you have a shorted pump it will heat up and draw more current without flowing.

 

[weather man]

Is there a fail safe to prevent this?