Fuel pump prime

[johnpbf]

I did a search and came across a bunch of fuel pump threads but nothing that entirely matched with my problem. I bought my totally stock 87 Grand National in October of last year and it took a while to start, the fuel pump would not prime, the seller told me the fuel pump needed to be changed and he gave me a brand new Walboro with the car.

My buddy and I installed it along with a new fuel filter and the car started right up every time. Well last week I did the MP3 input radio upgrade and added a USB port in the ash tray, I ran a ground and ran the power for the USB to the turn signal B/U light fuse.

I also had my battery tender hooked up because the car sat for a while and I had the door open while I was working on everything. While the battery tender was hooked up I bumped it and the negative clamp came off of the fender ground, I put it right back on and finished everything.

When I tried to start it up it cranked and cranked before it started, just like before. Now the FP is no longer priming, I checked the FP fuse and it is good. The Walboro pump is 4 months old and has about 30 miles on it.

Could I have possibly hurt something with the FP? Any ideas would be greatly appreciated. Thank you.

 

[DavzGN]

Fuel pump relay is probably bad. If the relay is bad, the pump doesn't turn on until a certain amount of oil pressure is reached

Sent from my SM-G900V using Tapatalk

 

[earlbrown]

Either the wiring is shoddy or the pump relay went bad.

Let the car sit overnight. Next time you try to start it with the extend cranking scenario, watch the oil idiot light. If the car fires up right when the light goes out, you're running on the back up system.

Also, the factory wiring won't support a stock fuel pump much less a 255L/hr pump, get a hotwire kit for it.


...and valve springs, and a timing set, and a new pump pickup, and a chip, and injectors, and some new rocker arm buttons, and bonus points if you toss the stock MAF and get a Translator.

 

[johnpbf]

Thanks for the reply guys. I was thinking possibly FP relay because it was fine one second and then suddenly "poof" the FP no longer primed. Call me crazy but could battery tender negative coming off of the fender while it was charging damage the FP relay?

When I bought it the original (35k miles) FP was bad and now after just 30 miles or so with a brand new Walboro I have no prime again, has anyone ever heard a gremlin in these cars that likes to fry fuel pumps? And if there were a problem with that wouldn't the fuse or relay pop first?

I'm still learning the quirks with these cars.

 

[earlbrown]

Fuses will only pop if there's a short or a component that causes a high current load. Bad connections or weak connections will cause a failure but won't cause the fuse system to get on the clock.

 

[johnpbf]

OK, just got home from work and had my son turn the key forward while I touched the FP relay, I heard and felt the relay kick on for about 2-3 seconds, then silence and that's what it is supposed to do, right? I still heard nothing from the FP in the tank. I read some about a hotwire kit, is that something that could possibly fix it? Also, is a hotwire kit really necessary for regular driving?

 

[GNRick]

How do you know the pump is not priming? Are you using a fuel pressure gauge? When my car was hard to start it was a signal that my MAF was about to fail. But the car did start.

 

[johnpbf]

How do you know the pump is not priming? Are you using a fuel pressure gauge? When my car was hard to start it was a signal that my MAF was about to fail. But the car did start.

No fuel pressure gauge. When the key is turned forward two clicks I can hear the relay click on and then off after 3 seconds or so but I cannot hear (or feel the pump with my hand on the tank). The car just cranks until the oil pressure builds enough pressure for the pump to kick on and then it runs just fine.

 

[dank GN]

Does the car run ? If so run it . My car has never primed then shut off . It's always just ran key on . It hasn't stopped me from driving the hell out of her

 

[johnpbf]

Does the car run ? If so run it . My car has never primed then shut off . It's always just ran key on . It hasn't stopped me from driving the hell out of her

It runs and I do drive it but I still want it to work properly. It should start right up and not crank for 10 seconds before starting.

 

[dank GN]

Cool I guess I have tuned my hard /coldstart with my sd2 chip . Anyway replace the rely and u should be good

 

[earlbrown]

Time to get out the test light or volt meter. If there is voltage coming out of the relay between the two clicks, you're relay is working.

If that line doesn't get hot until the oil pressure switch back feeds it, you have a bad relay.



Oh, and if there's not power going IN to the relay, you have problems upstream from there..

 

[GNRick]

Can a relay get flaky and quit sending power? My car was a little hard to start today, then died out at a stop light 10 minutes later. It cranked and cranked and finally started. Fuel gauge showed 0 psi until it started. Can a new relay be purchased at the parts stores and if so what specs should I look for? Sorry to hijack.

 

[GNRick]

Ok I see oreilys has one for $13, or Casper's for $25.

 

[earlbrown]

Can a relay get flaky and quit sending power? My car was a little hard to start today, then died out at a stop light 10 minutes later. It cranked and cranked and finally started. Fuel gauge showed 0 psi until it started. Can a new relay be purchased at the parts stores and if so what specs should I look for? Sorry to hijack.

Not really. They either work or they don't.


I'd start looking for bad connections and/or a tired trigger setup for the pump.

 

[TurboBuRick]

The ecm can loose the fuel pump signal. Time to get out the test light.

 

[GNRick]

Yes it could be the ecm. I googled symptoms of a bad fuel pump relay and this is what I got. Says the car could shut off soon after driving it. And could be hard to start. http://www.doityourself.com/stry/4-signs-of-a-bad-fuel-pump-relay

 

[GNRick]

The ecm can loose the fuel pump signal. Time to get out the test light.

Car was running fine with new fp relay then died at gas pump while idling. Checked voltage at pump and it was like .25 volts. Replaced ecm (I carry a spare of most parts now) and car started up. Drove 150 miles with no issues. Thanks Rick!

 

[johnpbf]

Time to get out the test light or volt meter. If there is voltage coming out of the relay between the two clicks, you're relay is working.

If that line doesn't get hot until the oil pressure switch back feeds it, you have a bad relay.



Oh, and if there's not power going IN to the relay, you have problems upstream from there..

Thanks for all of the info. I'll try a new relay tomorrow.

 

[johnpbf]

I tried a new relay this morning and the same thing happened, I could hear it click once and then click again in about 2-3 seconds but the car just cranked for about 10 seconds when I tried to start it. I turned the key off and then back forward again and it fired up after about 5 more seconds. The FP must obviously work if I am able to drive the car with no problems after it starts but it seems like the prime signal is not getting to the pump from the relay.
I though I read somewhere that I can jump a wire across the relay connector to see if that runs the pump. If I remember correctly the guy that posted it said "there are three blades in a row and one at 90 degrees of the rest, jump the middle of the three with the one at 90 and the pump should run with the key on" he also said he runs his car like that. I'm wondering if that will show me if the FP is receiving the signal or not.
I just wanted to double check that before I try it.

Thanks