Fuel pressure problem

HUENEMEGN

Active Member
I can’t seem to get fuel pressure when I turn key to ignition on ?
When I crank the car to start , then it will pressurize and start the car , idle and run like normal . I’m guessing it’s running off the Oil pressure switch .

It’s a new build. I’m in my break-period so just driving around with low boost . My previous engine I would have fuel pressure with key on . Not anymore .

I went with E85 on this build so I got a new DW400 pump with a different hanger. 120# injectors . I changed to a new diaphragm on my Kenny bell fuel pressure regulator.it also has -8 &-6 fuel lines .

So far I have checked the fuse on the fuse box...It’s okay .
I’ve replaced the fuel pump relay with a new one . The one on the fender ...no change.
I’ve check pressure with another gauge .... No change
I thought it was my hot wire so I switched the tank wires back to stock and bypassed my hot wire ...No difference.

I just tried adding power to the fuel pump via the connection behind the alternator and I got fuel pressure! GREAT !? but when I did that , I here some sort of pressurized noise around the fuel injectors area. Are they spraying ? It sounds like they are . As soon as I stop touching the alternator terminal to give it power , my fuel pressure drops back to Zero . What can be going on ? I pulled a plug . Looked kinda wet . I put it back and tried starting the car , it was having difficulty this cold start . It eventually started . Ran her for a minute or two , rechecked the same spark plug , looked dryer than when I first pulled it .

so can my injectors be leaking ?
The injectors ( Precision) I bought used but service at Fullthrottlespeed and shipped directly to me from Fullthrottle. Do they give the customer a test print out ? Just got a recipe. Anyhow


Some more info ... when I purchased the DW fuel pump from a member here , it was new in wrapper . But it came with a new but use fuel hanger . I never asked if it was for a digital car ? Mine is analog. Wasn’t sure if that can cause a problem. I will post a picture of the side by side hangers .

Any help would be appreciated.
 

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HUENEMEGN

Active Member
Have you looked at the oil pressure plug (by the oil filter) ? could be as simple as it came off.

I have checked it . It’s connected. I think that’s how it’s getting fuel pressure as oil psi rises to 4. A second or two of cranking , It starts right up.
 

John Larkin

Sublime Master of Turbology
I think there is something going on with your Kenny Bell regulator. Injectors can't pass fuel unless they get electrical signals from the ECM and then open/close rapidly, ticking like a timer. You say you are hearing a spraying sound. Do you still have your stock regulator you could swap back on and see if that fixes the basic issue? E85 is sometimes a hard start but never more than an extra turn or two of the engine unless it is really cold out. I would start with the regulator swap first. Maybe the E85 ate the new diaphragm and is causing fuel to just bypass but the big fuel pump is masking that issue. Or the diaphragm slipped out of place?
 

HUENEMEGN

Active Member
I think there is something going on with your Kenny Bell regulator. Injectors can't pass fuel unless they get electrical signals from the ECM and then open/close rapidly, ticking like a timer. You say you are hearing a spraying sound. Do you still have your stock regulator you could swap back on and see if that fixes the basic issue? E85 is sometimes a hard start but never more than an extra turn or two of the engine unless it is really cold out. I would start with the regulator swap first. Maybe the E85 ate the new diaphragm and is causing fuel to just bypass but the big fuel pump is masking that issue. Or the diaphragm slipped out of place?

I hear ya. I don’t have an original regular. I still have the old diaphragm form the regulator that at I can put back . I’ll See if that works since it was working before this .rebuild . I will try than them report back .
Thanks
 

salvageV6

Daily Driver
A simple test with a voltmeter or test lamp on the dark green white stripe wire at the fuel pump relay will tell you if the ECM is working to trigger the relay.

Pink/blk striped wire should have power on it also continuously with key ON test.

Prime on the dark green/white stripe wire only lasts a couple of seconds so extend the meter or test lamp leads to the windshield so when you turn the key to the ON postion you can read it quickly.

The black/white stripe wire at the relay should have ground on it at all times, easy check with a meter or test lamp.

Relay output wire is gray I believe or tan/white stripe (last wire to test onthe connector) and if the trigger signal tests okay as well as key ON for the pink/blk wire you can check the relays output with the meter or test lamp on that wire.

Shouldn't take more than 15 minutes to test all four relay wires after you get the meter or test lamp wires extended.
 

HUENEMEGN

Active Member
Okay . So far I went and checked the relay at the connection With a test light . I touched the green/white wire , I get power but with no key in the ignition? I turn key to on , it shuts of the test light off . Weird . So I checked all the other pins and they all have power with key out of the ignition ? Now I’m confused.
 

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HUENEMEGN

Active Member
I just went to test the fuel pump sending unit connection behind the back bumper . So I tested this one with a volt meter . I tested the tan/white wire and I got .03v when I turn ignition to on. It was stead and did not drop after 2 seconds. I went ahead and tried the red wire and I got 8.26v key on . Steady as well.

I also went ahead and replaced the diaphragm on the regulator ...No changes .
This time I had a helper listen on the passenger side of fuel rail since I heard some spaying like noise inside the intake manifold. I think it’s coming from the fuel return line when I jump the fuel pump behind the alternator .
After jumping the Fuel pump and seeing good pressure on my gauge , it drops back to zero when I let go of the jumper connection .

Still confused on what to do next .

One more thing I forgot to mention if it helps ... I did a AC delete before installing this new build . I took the whole AC unit off . Hopefully I didn’t accidentally cut some wires associated with the fuel system .kinda was a bitch to get out. Lol
 

Anthony P

sharing knowledge with those who care to listen
I don't remember wiring diagrams or color of wires without the diagram in hand. but what caught my attention was when you said,
"After jumping the Fuel pump and seeing good pressure on my gauge , it drops back to zero when I let go of the jumper connection . "

fuel pressure should remain in the rail for about 30 minutes or so. if it's not as you saw today...injectors leaking down? fuel pump check valve bad? rubber hose from fuel pump to sending unit port messed up? for pressure to drop that quickly after the pump stops sounds like check valve or hose to me.
 

HUENEMEGN

Active Member
I don't remember wiring diagrams or color of wires without the diagram in hand. but what caught my attention was when you said,
"After jumping the Fuel pump and seeing good pressure on my gauge , it drops back to zero when I let go of the jumper connection . "

fuel pressure should remain in the rail for about 30 minutes or so. if it's not as you saw today...injectors leaking down? fuel pump check valve bad? rubber hose from fuel pump to sending unit port messed up? for pressure to drop that quickly after the pump stops sounds like check valve or hose to me.

You are right .pressure should hold for at least 30 minutes but it dont . As soon as I stop the engine it drops right away to zero . When I disconnect the fuel pump jumper , it drops to zero .
The injectors where just service before I fired up the engine . They were at Fullthrottle . I’m sure they would check that right ?
 

Anthony P

sharing knowledge with those who care to listen
I would expect Mike or Steven would've seen a faulty injector during servicing. seems like pressure is dropping too fast for a leaking injector. kind of like shutting off the garden hose at the hose bib with the other end open. pressure is gone in an instant. that sounds like check valve in pump is not working correctly since you already went through the fuel pressure regulator.
 

HUENEMEGN

Active Member
I would expect Mike or Steven would've seen a faulty injector during servicing. seems like pressure is dropping too fast for a leaking injector. kind of like shutting off the garden hose at the hose bib with the other end open. pressure is gone in an instant. that sounds like check valve in pump is not working correctly since you already went through the fuel pressure regulator.

Yes , the pressure drops down to zero instantly after I shut down the motor .
Do you mean the check valve in the pump or the hanger? The pump was brand new , the pump hanger looks almost new .
 

Anthony P

sharing knowledge with those who care to listen
hanger is just tubing. check valve would be in pump.

I think you just identified the problem and the solution with that TSB. hopefully the downtime is short while DW installs a check valve.
 
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