The Mighty Texan

iTrader: (4)

I have another thread going as i have been having some other issues, which makes me think my problem might be electrical.

I turn the key, i hear clicking from the relay but no buzzing sound that i used to hear from the fuel pump priming. First things first, i checked fuses and relays and swapped with known good ones, nothing. Checked the schrader valve, not even a hint of pressure. Where do i go from here? Thanks guys!

TurbopigB4C

iTrader: (5)

You need to check for power and ground at the fuel pump connector when the key is turned on. If you have both you need a pump. You can also use a hammer and bang on the tank with the key on and see if the pump turns on. This also means you need a pump.

The Mighty Texan

iTrader: (4)

Where is the fuel pump connector located and how do I check that it is grounding?

The Mighty Texan

iTrader: (4)

This morning i went out and the fuel pump primed and it ran fine, however it soon got to the point of suttering and running bad. I keep turning the key and it primes everytime. However, when starting the car it still runs bad each time also.

PPI Typhoon

iTrader: (1)

I've had it happen before where my fuel pump works cold, but when it heats up, it dies and cannot restart until it cools off. Sounds like you need a new pump.

The Mighty Texan

iTrader: (4)

I called Napa and they said the gm replacement (they said the whole system w/e that means) was $480 or something like that. And the Walbro 255 i see that alot of people get on here is close to $100.

TurbopigB4C

iTrader: (5)

You sound like you are kind of lost from this post and your other post. From what it sounds like you have a bad fuel pump. It is very common for it to work sometimes and not work others. If it is also weak it could be the cause of your misfire. I hate saying to shotgun a pump especially since I am not there to check it and it sounds like your broke. The pump you get from GM comes with the entire sender assembly while the racetronix or walbro only comes with the pump and requires you to disassemble the sender assembly and modify it slightly. There is a sticky on this if you are confused. Also keep in mind if you replace just pump I have noticed from experience the sender seems to go bad soon after replacing just the pump so your gauge might stop working if you replace just the pump. If you are going to do heads+cam or anything major in the future you need to do the 255lph pump though. Also the install done the correct way is not for a novice on the ground. It is not too bad but from experience if you do not have a lift and do it on the ground I usually remove the entire rear diff because I don't like jacking the car up super high because it makes installation of the tank harder because its higher. You also must lower your exhaust or remove it to get the tank out. Your other option is to butcher your car by cutting an access hole in the trunk floor.

TurbopigB4C

iTrader: (5)

The connector is above the fuel tank in the rear of the car. You use a multimeter to check with a wiring schematic.

The Mighty Texan

iTrader: (4)

I read some of the write up's on replacing the fuel pump and it seems like i should be able to do this myself.. I have the exhaust dumped so its clear out of the way, i have about 10 gallons or so in the tank still however, and i also don't have access to a lift or anything, i normally just drive my car on blocks. Is there an easy way to check to see if the pump itself is going out or if its an electrical issue or something else thats causing this? I banged on the tank with a hammer while it was running poor and it didn't affect anything.

TurbopigB4C

iTrader: (5)

Its common for the pumps to go out. If its still running try to get the tank almost to empty it will make it much easier. Go to harbor freight or online order a fuel pressure tester. When its running bad check the pressure. You also want to make sure the pressure is holding. When you turn the car off with gauge connected the pressure should stay up and not drain back rapidly. The hardest problems is when things still work just not right. Its much easier to diag things when they are completely broke. When your car will not start at all have your fuel gauge hooked up and if you have no pressure you are pretty safe in knowing its the pump.

The Mighty Texan

iTrader: (4)

Ok I FINALLY found someone with a fuel pressure tester that wasnt inline. (Been trying to find one for a while now actually) Anyways, fuel pressure is constant priming and running, and when throwing the misfire code at 55lbs. How long should the pressure be holding for?

TurbopigB4C

iTrader: (5)

Is it actually misfiring or just has a code set? Is the fuel pressure tester long enough to tape it to the windshield while you drive? You could be losing fuel pressure only under a load. Like I said before its much easier to test when the car will actually not start at all. When it wont start check fuel pressure. The pressure should only bleed back very slowly once turned off, like a few pounds in 10 minutes. If it does not bleed back that doesnt eliminate the pump as the problem its just a common reason why fuel pumps will not allow the car to start in the morning and then after a while they will start. You could have multiple problems with your car but focus on one thing at a time. I would go after the crank no start problem first because they could be related and a crank no start is easier to diagnose if you already replaced your plugs and wires.

TurbopigB4C

iTrader: (5)

Also is it a dead miss. a fishbite / nibble, or do you not feel it misfiring?

The Mighty Texan

iTrader: (4)

I can feel it shaking and running bad when its missing and the code comes up. I hooked a scanner up and am getting a P0200 (injector circuit voltage variation error) as well as the p0300 (random misfire) code. The pressure in the gauge bleeds down to 0 pretty fast after the car is shut off Probably 2-5 min. I don't really know how to diagnose the crank no start anymore because it is priming and starting now.

The misfire seems to come apparent the longer it idles, it also while driving, will flash sometimes and then just stay steady on the SES light, it feels that the misfire is constant for the most part however.

The misfire will shake the car and the shifter pretty noticably and also stumble and become more obvious under acceleration, it will bog down and shake a bit more. The engine RPM's aren't very affected by this misfire however, just mainly you can hear it and it feels off balence

TurbopigB4C

iTrader: (5)

If the pressure bleeds down that fast there is only two options you have a bad fuel pump check valve which requires replacement of the pump or a leaking fuel pressure regulator. Pull some plugs and see if they look wet with fuel. If they are its a bad regulator and that means you should change the plugs at the same time because they would be fouled. If you change your regulator and the fuel pressure still bleeds down that fast then you have a bad fuel pump for sure. With it having an intermittent crank no start I lean towards a bad fuel pump but it could just be having a hard time building pressure because the regulator is bleeding off the pressure. The regulator is cheap and easy to replace so if you are unsure I would do that first.

I would need to see the flowchart and code description from the service manual for a p0200. That is not a very common code and in my four years as a GM tech have never had one set. I would start with the fuel problem since we know that has a problem.

The Mighty Texan

iTrader: (4)

I recorded the drop of fuel pressure from the turn of key. 58lbs at running, turned car off, 45 at 10 seconds, 35 at 20 seconds, 25 at 40 seconds, then it slows down and drops to 10lbs or so at around 3-4 min, then absolutly 0 at around 7-8 min.

I pulled the plugs (after i had ran it, and they look just like i put them in yesterday, no buildup or being wet.

I don't know how long the system is supposed to stay pressurized, if read people with different cars saying theirs held 60 for a week, some saying it went to 0 in about 5-10 seconds of turning the car of, etc. Could a leaky injector also cause the fuel to lose pressure after being off? The running and idle pressure stay constant at 58lbs.

Thanks for all the help so far Turbopig!!

The Mighty Texan

iTrader: (4)

A bit later and after the car had sat for a bit, i messed with and jiggled some of connections and wires with the wire harness around the pcm and to the injectors before i started it up again. The car started and ran fine and came up to temp the same, so i went for a drive and it ran like a champ. Monitored codes with the scanner and a 0140 (O2 sensor bank 1 sensor 2) came up as pending and never threw an acual code or SES light. I ran it hard and had some fun with it since i haven't been able to in a while and she did great. Came back and checked for codes or bad idle and nothing. Also started it up again and same thing. We'll see how it stays... i'm assuming either the pcm or wiring is the problem..

TurbopigB4C

iTrader: (5)

Good luck with it. It sounds like your misfire was a loose connector. If the fuel pressure bleeds back that fast it means you have a bad fuel pump. Its very common for it to happen. I have seen new trucks with only 5000 miles have it happen and I would replace them under warranty. Your pump may still work but when it bleeds pressure back that fast its a sign that it is about to fail completely so its up to you whether you want to replace it now or wait for it to go out completely.

The Mighty Texan

iTrader: (4)

Ok thats what i presumed, probably get replaced here in the near future. Thanks for all the help!

CamaroZ28_LS1

iTrader: (5)

had the same issue as of in my Z28 and my SS. Found burned wires on the harness side of the pump. Looks to be from High resistance in the wires and causing the pump to fail. I threw in a Walbro pump and it cured the problem. Only issue I have now is my car won't stay primed at the rails on start ups which can be annoying. Anyone else have this issue with the non venturi tube style walbro pump? If there is a fix I can easily open my "Access Hatch" lol.