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Discussion Starter #1
5.3 turbo. bosch 210's, magnafuel 750 pump and reg. just had injectors cleaned. go to the track last night make a pass car runs great. engine starts to stumble in the shut down.. eventually stalls, coast of track. hit key, starts for a second and shuts right off. fuel press is down to 30# we run it at 43. wait a while try to start it same thing. then it does start and runs real rought and wideband is super lean. put it on the trailer and come home. get home from work today car fires right up and runs perfect with 40# pressure. pulled the pre filter and its fine.
im on a stock computer and pump is on a toggle, so the computer does not control the pump... pump going bad? 12 passes on it. thoughts? oh, its on E85
 

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No relay straight off toggle switch??
Voltage??
Do you run an alternator??
How much boost??
Big electric pumps are notorious for crapping out and not being very reliable especially at elevated pressures required by forced induction. Anything at or over 1K hp needs a mechanical pump on it IMHO. There are some new badass electric pumps on the market over the last couple years but ridiculously expensive and I still wouldn't trust them like a belt or cable drive pump. Good way to kill an engine especially with an ECU that doesn't have safety system to keep from melting it down in the middle of a pass.
 

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Discussion Starter #3
pump is on a relay
yes, running an alternator.
14 volts
was on 20#'s last night.

this car has ran fine all last year with no changes

also, when i did get it to fire and it was running rough, the tach needle was bouncing erractically
 

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May try a new or known good crank sensor. Is it a gen 3 or gen 4 cam sensor setup??
 

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It won't I was thinking more about the very erratic idle but it could also have just been running out of fuel at the injector being down 13psi on pressure. Sorry just thinking out loud.
 
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I know this sounds crazy but I would check the wiring. It sounds to me like a loose ground or loose connection.
 
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^^^X2^^^
A "heating" connection acts exactly like a resistor in the line lowering the voltage to the pump. Better if you find it first before it starts a fire. In many cases they won't blow a fuse or trip a breaker and just sit there cooking the connection until it finally crystallizes everything and fails completely. Good call Darren.
 
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X3 ^^ good 40 amp or better relay and good 10 gauge or better wiring. I run a 4303 and a 4703 and use a leash electronics 70amp relay board for both with 8 gauge wiring no problems
 

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Discussion Starter #10
its wierd because it has ran fine since i came home from the track. ive looked at all the wiring on the pump and from the battery. yesterday i pulled both filters and cleaned them. (didnt look bad) but does sound a lil more crisp. verified voltage, its at 14.2 with everything on and running. car is running perfect now. dont know what else to look at
 

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That sounds to me like a loose wire, a bad crimp, if anything is soldered that's a problem in itself on a race car, etc.
Sounds like a voltage issue. Was the alternator charging the batter when this occurs? I have seen this recently and it took several days on the dyno to show it's face but when it did it was exactly what you are describing. It turned out to be a bearing in the alternator that would expand only after a bunch of run time (heat). Also, like these guys said, most of these pumps require around 30 amps and most people simply do not have the wiring up to snuff. Other thing to make sure is it's not sitting a long time with ethanol in the tank. That alone will cause all sorts of issues.
 

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Discussion Starter #12
i pulled both filters and cleaned them again. back together it had 40 psi. removed the elements and pressure went up to 47. called magna fuel, he doesnt like my 6 micron element before the pump and recommended a 75 micron. told me to run a 40 after the pump, which is what i was running. i ordered 2 new elements. he also said theres a possibility the needle brgs in the pump may have stuck when it was acting up.
 

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I have been reading some other post on other forums with similar problems and it could also be if you have foam in your tank that the pump could be sucking the foam towards the feed fitting coming out of the cell and causing a restriction. also check to make sure your return hose is flowing freely into tank or cell. just some other ideas to check.
 

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Discussion Starter #14
went to the track tonight. made a pass, ran what it should have and stumbled and shut off on the return road. it would start for a second and shut right off. fuel pressure was good. let the car cool down for an hour and a half, fired right up and ran perfect.. now im leaning towards a sensor with a heat issue... any thoughts?
 

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went to the track tonight. made a pass, ran what it should have and stumbled and shut off on the return road. it would start for a second and shut right off. fuel pressure was good. let the car cool down for an hour and a half, fired right up and ran perfect.. now im leaning towards a sensor with a heat issue... any thoughts?
COP or Distributor if distributor could be a pick up in it going bad or a sensor?
 

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i pulled both filters and cleaned them again. back together it had 40 psi. removed the elements and pressure went up to 47. called magna fuel, he doesnt like my 6 micron element before the pump and recommended a 75 micron. told me to run a 40 after the pump, which is what i was running. i ordered 2 new elements. he also said theres a possibility the needle brgs in the pump may have stuck when it was acting up.
Damn , that pump must have been struggling with a 6 micron before the pump .

100 micron is the norm for pre pump .

I would go 10 micron post filter if running injectors . I had a pump fail and i was using a 40 micron because I wanted to be able to clean it instead of replacing the 10 micron paper element .

The trash got past the 40 micron and clogged all 8 injectors .
 

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Dont buy cheap filters either . They are not created equal .

Aeromotive makes some good filters with a lot of surface area .
 

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Discussion Starter #19
Damn , that pump must have been struggling with a 6 micron before the pump .

100 micron is the norm for pre pump .

I would go 10 micron post filter if running injectors . I had a pump fail and i was using a 40 micron because I wanted to be able to clean it instead of replacing the 10 micron paper element .

The trash got past the 40 micron and clogged all 8 injectors .
for sure. i have a 75 pre pump and a 40 after in it now. my tuner is leaning towards the MAP sensor as it only seems to mess up after being in boost for a while
 
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