High IAT fuel pump shut down

[Mike M]

About a month ago my car stalled at a traffic light, I was watching my ScanGauge and noticed when my IAT temps got to about 130 degrees my fuel pump would shut down.

It seems like my FPDM was going into thermal shut down.

I got a modified FPDM and today it happened again. This time the IAT got to 146 degrees and it happened again (at the same dam traffic light!!!). I got it home and let it idle in my hot garage and waited for the IAT to get to 146 and sure enough the fuel pump pressure went from the 50's down to the 20's and of course it died.

I believe the modified FPDM helped but not sure where to go from here.

May not be a problem when temps cool down but that isn't really a fix.

[Limited360]

With intake temps that high you may be boiling your fuel in the rails... is this on 93 octane 10% ethanol or 85% ethanol?

Do you know what the FPDC (Fuel Pump Duty Cycle) is at when this occurs?

Are you running a boost a pump on the Stryker 340 pump?

Are you running OEM power wires for the pump?


I've seen cars not start due to high underhood temps boiling the fuel in the rails, makes injecting it a rather difficult task!

[Mike M]

With intake temps that high you may be boiling your fuel in the rails... is this on 93 octane 10% ethanol or 85% ethanol?

Do you know what the FPDC (Fuel Pump Duty Cycle) is at when this occurs?

Are you running a boost a pump on the Stryker 340 pump?

Are you running OEM power wires for the pump?


I've seen cars not start due to high under hood temps boiling the fuel in the rails, makes injecting it a rather difficult task!

I run 91 octane (that's all we have out here) and I run 5 gallons of E85 in the tank every fill up.
I never installed my boost a pump

All wires OEM.

Don't know what the duty cycle was at.

I do know the fuel pump pressure dropped to 20 before it died.

Wondering if it is the fuel boiling in the rails is the E85 aggravating it or helping it.

I may stop the E85 as a test. I do run Meth Injection so the 5 gallons of E-85 probably isn't needed for octane.

[Marauderjack]

Mike......

I am guessing here but I suspect the Ethanol (E-85) is your culprit in that it vaporizes at about 170*F and the fuel system is set up for gasoline which has a higher vapor pressure and probably a higher boiling point??

Effectively you are getting "Vapor Lock" in your fuel system.....I think??

Go back to just gasoline or 10% blend and see what happens!!

BTW...where are you that you have 146* IAT's......."Earth" is a big place!! I seldom see IAT's of 125* and it's H-O-T here in Beaufort!!

Good Luck!!

[justbob]

Mike......

I am guessing here but I suspect the Ethanol (E-85) is your culprit in that it vaporizes at about 170*F and the fuel system is set up for gasoline which has a higher vapor pressure and probably a higher boiling point??

My under hood temps have melted and warped my MAF and my JLT tube and no issues here (besides the obvious heat) Still on the stock wiring, stock FPDM, BAP hooked up to Trilogy's specs, -8 feed, and 340 Aeromotive.

Effectively you are getting "Vapor Lock" in your fuel system.....I think??

Go back to just gasoline or 10% blend and see what happens!!

BTW...where are you that you have 146* IAT's......."Earth" is a big place!! I seldom see IAT's of 125* and it's H-O-T here in Beaufort!!

Good Luck!!

Self proclaimed Builder Of Badassery.

Buy it, Break it, Build it BETTER.
"Since 2004"

[sailsmen]

My IAT is located in my intake manifold resulting in high closed throttle temps and my pump is not shutting off.
The higher fuel pressure is to increase the boiling point. I assume the temp in fuel rails is lower.
Where is your IAT located?

[Mike M]

Mike......

I am guessing here but I suspect the Ethanol (E-85) is your culprit in that it vaporizes at about 170*F and the fuel system is set up for gasoline which has a higher vapor pressure and probably a higher boiling point??

Effectively you are getting "Vapor Lock" in your fuel system.....I think??

Go back to just gasoline or 10% blend and see what happens!!

BTW...where are you that you have 146* IAT's......."Earth" is a big place!! I seldom see IAT's of 125* and it's H-O-T here in Beaufort!!

Good Luck!!

Next tank will be without E85, Arizona

[Mike M]

My IAT is located in my intake manifold resulting in high closed throttle temps and my pump is not shutting off.
The higher fuel pressure is to increase the boiling point. I assume the temp in fuel rails is lower.
Where is your IAT located?

It is in my M.A.F.

Not sure if the pump actually shuts off or if the possible vapor lock is causing the fuel pressure to drop with the pump running. I will have to look at duty cycle next time.

[RacerX]

The 340s draw a lot of current and the wiring should be upgraded for one. Typically the PCM will raise fuel pressure with high IATs and pull a little timing. Higher pressure helps slow boiling and the injectors just have shorter pulses with the increased pressure. Upping pressure will draw more current. Upgrade the wiring imho.

[Mike M]

I will look into that ...thanks

[Limited360]

Yeah my guess is that your drawing too much current through stock lines when the pump is trying to keep the pressure up to avoid vapor lock....

Try monitoring the FPDC and just let it idle at home till it shuts down again

[sailsmen]

Assuming your MAF is located before the throttle body you should not be seeing IAT temps of 146. Something is wrong.

[Mike M]

Assuming your MAF is located before the throttle body you should not be seeing IAT temps of 146. Something is wrong.

That's what I though but it is in my maf. Don't know what I could do to change it's temperature.
It was 108 yesterday and driving down the road it was about 128 - 130 but it creeps up at idle.

[RacerX]

Those temps are at the MAF? You're sucking in a lot of engine heat. Me too.

[sailsmen]

Do you have a blow thru MAF and are you venting to atnos?

You may want to look at a way to reduce any engine heated air.