Fuel pump won't prime with key "ON" but will with EvoScan...
 

After a month and a half of having starting and idle issues and replacing multiple sensors(all under $50) on my new build, I realized that the fuel pump isn't priming with the key in the "ON" position as I forgot that it should and never though of it being an issue as the car would start....sometimes. The interior is stripped at the moment and it's very obvious when it's priming. I put the fuel feed line in an empty water bottle and turned the key to "ON" and not a drop came out yet sent fuel fine when cranking the engine. It's a 10 year old Walbro 255 that was used for a very short period in another car and was swapped to the Evo in '04. It was sitting in the tank for about 2.5 years without any use whatsoever before the car was messed with after an engine failure.

A few weeks ago, I used EvoScan to prime the pump to drain the fuel tank to put in more fresh gas and it worked fine then. I pulled the pump earlier and it was covered in rust on the bottom as well as the sock and that new fuel looked rusty as well. I have a bunch of pics of this I'll post here tomorrow. Used a test light to see if the pump was getting power with the key on and it was.

Question is what would cause the pump to not prime with the key on but will when using the fuel pump prime actuator on EvoScan?


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if the pump was getting power (and the ground was good), but not running then the pump is bad. sometimes when they go bad they work intermittently before they totally die.

Use a volt meter to test the pump. If the meter shows a good signal I would start checking the wiring from pump to fuse box. You could have a short or bad fuse. Just my quick two cents.

Thanks for the fast responses. I'm already looking for a new pump, after you see the pics, you would agree to replace. May go bigger but anything to get the car on the road will be fine at this time. May even take the factory Evo pump out of my 240sx and put it in for now depending on its condition. Just hope that a new pump will be the end of the cars problems.

Pics added.

My fuel pump didn't prime with the stock ecu.

I noticed the same thing about 6 months ago. My car stopped priming with the key on. Then people here told me this pump is only gonna prime if it has to (which I know is not the case) so 6 months later I'm still running the same pump. Car starts up perfectly fine every time. I've been watching my wideband while driving around and ESP WOT pulls. But it doesn't seem to have any other prob then not priming. My pump is almost 5 years old and has 87k miles on it. I think it's time for a new pump for my next tune

I keep hearing mixed answers on this. The stock pump is quite and the Walbros are loud. The fact that the fuel system gets no pressure until the engine is cranked over is odd to me. From what I've been reading, it should prime and be heard with the key on but I don't remember. Either way, the pump is getting replaced as that rust isn't good, its already turned that fresh gas into a muddy color and the sock is nasty.

I never payed attention to whether it primed or not until I installed my Deatschwerks 300. After installation I tried to prime the fuel system before the first start up and couldn't get the pump to prime without cranking the engine. If my pump were priming, you would be able to hear it. I have aem now and it primes for 2 seconds every time the key is turned to the on position. It's very loud. If I were you, I wouldn't worry about it. I guarantee my pump was not priming until I cranked the engine on stock ecu.

wow that pump looks awful! i would replace it and drain/clean the tank.

I will be draining the gas again(3rd time), any special way to clean/rinse the tank out?

I debating on taking the tank out to clean it but it looks very involved after looking at the service manual. Is there any produce that I can mix with water to fill up the tank and let it sit for a bit before draining?

I ordered another low mileage Walbro and 2 new filters to keep everything clean until a few tanks of gas are run through the tank.

I am having same problem, my car has been sitting for about 2 years. I had no idea that the pump would look that bad. I guess I'll check mine as well.

Honestly, I've seen a few cases in which the Walbros just didn't prime with the key in ON position, but still got fuel to the rail to start the car up when cranking it over. Did anything come out in the water bottle when you tried cranking it?

I would check it for sure. Gas gets watered down after sitting that long. It took me hours to clean the rust out of both sides of the tank and it most likely still has some left in there. I bought several fuel filters to change out over the next few tanks of gas.