The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Rix Racing
Please Support STM Tuned

2G No fuel pressure when it's below freezing

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

1kick

5+ Year Contributor
84
17
Mar 27, 2018
Santa fe, New_Mexico
Hey guys my car won't start when it's below freezing temps. I'm getting no reading on the fpr I can hear the fuel pump priming it usually takes about 5 seconds to prime but when it's cold it primes for about a minute but builds no pressure it has an aem series 1 ecu walboro 255. it does start mid day and afternoon when temps are above freezing do you think it's the fuel pump the ECU or the tune thanks for your help
 
was the relay clicking on and off?
if it was, try swapping out the relay. if that doesn't work check the ground, if thats good, next time it won't start, check to see if its getting voltage at the (+) side of the coil (86 on the diagram).

You must be logged in to view this image or video.
It definitely sounded like it was. Can cold weather affect a relay? I'm leaving it here at work tonight I'm sure it will act up in the morning. I will test power and ground I just hope the ECU is sending a signal
 
Relays are electromechanical, so I would say yes, they can be affected by temp. Even the completely transistorized flasher unit can change flasher speed in cold temps. I know because mine did, to the point where around 5F it would simply stick on when I used the turn signal. A new unit solved the problem, and now flashes the right speed all the time. Interestingly I never heard of this problem with the old-style flasher units that used a bi-metal strip, though in principal they would be all the more susceptible. I would take the advice of swapping in a "known good one" (if you can find such a thing), and see if it fixes it. Sometimes that's the easiest way, and more often with electrical/ electronic parts.
 
I believe at this point in the story -- 'can't start' caused by freezing but not apparently due to water in the gas -- I'd go back to a stock fuel pressure regulator if that's an option. Once you have absolute proof of where the trouble is you can choose the best next step.

I've cut open a stock FPR. The valve itself is a disk, pressed against the opening to the rail. A spring pushes on that disk so it only lifts when the rail pressure exceeds the pressure from the spring. A diaphragm pushes the other end of the spring: High vacuum means less spring pressure means less fuel pressure. I can't see how water on the vacuum side could do any worse than lock the thing at some pressure setting between minimum and maximum while water anywhere between the inlet from the rail and the outlet to the recirc. line would at worst stick the thing at maximum pump pressure. Either way the engine will start and run.

One thing about OEM parts: they have been very thoroughly tested, not just at test facilities in every conceivable climate but also in many millions of miles of ordinary driving. Weird possibilities like water getting in from the vacuum side are not 'gee, we never heard of that happening.' Either they can't happen or someone knows about them.
 
Just an update the pump I heard was my water meth pump that I'm not using so I removed it. I did put a gallon of ethanol fuel in with about half tank of gas still the same fuel. The car is starting in the mornings but the temperature has not been as cold when the temps dip down again I will post an update
 
It's back to not starting I'm not getting a signal from the ECU also swapped relay is there a setting in advanced startup I need to look for or is the ECU shot
 
AEM V1 fuel pump setting are in Options -> Configure Outputs on the 1310 box. AEM connects the fuel pump to LS11 unless someone modified this.

You must be logged in to view this image or video.
 
AEM V1 fuel pump setting are in Options -> Configure Outputs on the 1310 box. AEM connects the fuel pump to LS11 unless someone modified this.

You must be logged in to view this image or video.
Are the values adjustable I will check to see what mine look like thanks
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top