Odd Fuel Pump Issue

[BattelWagun]

The other day my fuel pump went out on me. I'm not surprised it had 120k on it and I run the tank to E all the time... Anyways, I got the pump replaced at a shop since I needed the truck back ASAP because the beater car isnt running to well these days. With the old pump (and I know for a fact almost all of these trucks) I would hear it cycle a few seconds before I turned the engine over and after I shut it off. The new pump doesn't do that! It's annoying as the shop said it's supposed to be like that (I'm pretty sure it's not...) and it makes starting harder now too. The engine used to start after maybe 1 second(id hear it turn over once) when it was warm. Now it takes a few seconds (turns over 3-5 times). I know nobody can diagnose this issue but I'm wondering if anyone has encountered the same problem because I know come next winter, it'll get to be a complete ***** to start like that.

 

[SunlitComet]

The initial 2 second run is triggered by the PCM to the fuel pump relay so if it does not do that but run with plenty of pressure after finally starting then I would suspect something screwy with your computer. Bear in mine I say this becuase My tech data says in '99's the pcm has total control of fuel pump relay unlike a couple of years earlier where the pcm did the initial pressure charge but oil pressure kept it running long term. not sure which year it changed over but both get the same results.

 

[BattelWagun]

well that screws me over haha. Not gonna be getting the pcm reprogrammed any time soon... It's been getting real hard to start too, almost 20 revolutions and then it barely stutters to life. No SES light either, this is pissing me off.

 

[SunlitComet]

I don't think reprogramming will help. it sounds like yours uses a oil pressure switch for running mode. My diagrams maybe overlapping between newer model years. In that case your computer might have lost it trigger output and cranking the engine builds the minimum oil pressure to activate the relay on its own. and the pump creeps up the pressure. the oil pressure switch for pump would have orange and grey wire.

 

[BattelWagun]

Allright well it looks like im going wire hunting this weekend! thanks a lot man, i hope thats the problem.

 

[SunlitComet]

this is for the one with a oil presuure switch controlled fuel pump.

 

[BattelWagun]

Much thanks for the diagram, you got some good shit sunlitcomet!

 

[SunlitComet]

forgot to mention on the above picture the relay is only use by the PCM for priming only so check that first. it may have faulted out.

 

[BattelWagun]

Alright so here's what I just did:
I unplugged the relay and tried to start it, no beans.
I started it and pulled the relay, and it died out. (hold in mind it wasn't warmed up yet, but oil gauge read 40 psi) I did however unplug what I think may be the fuel pump switch, there is a black block near the front drivers side that has a fuel line from the frame going in, and a line going out to the injectors. on this block is an electrical box with a plugh that has what appears to be a weather ridden grey and orange wires. I unplugged that, it had no effect on the engines behavior whatsoever. Let me know if you want a picture, i took one because it's hard to explain.

 

[SunlitComet]

yes please so I can match up with data and clarify the data.

---------- Post added at 06:26 PM ---------- Previous post was at 06:21 PM ----------

also those color are the power feed in and out on the fuel pump relay. that was not the one you pulled out and died is it? Pictures are good right now. will look for the fuel rail switch you decribed.

 

[BattelWagun]

Ok, you'll have some pictures tomorrow then. I realized the one I took is not helpful whatsoever because its just too close up.


Sent from my iPhone using Tapatalk

 

[BattelWagun]

Okay here ya go. The first two are of the actual unit I'm talking about with the fuel lines in it. There is a feed from the tank connected to the top and a line coming out the bottom that goes somewhere on the intakemanifold. The third picture is of the plug I'm talking about, when unplugged it makes no difference with the starting/running behavior of the truck. And the last pic shows where that connection goes. If you need any more explanation etc. Just let me know.

 

[SunlitComet]

Sorry to burn yours beans but that is the Evaporative (EVAP) Emissions System for fuel vapors which does not address the pump issue. I am afraid we are back to square one.

---------- Post added at 07:53 AM ---------- Previous post was at 07:50 AM ----------

So before the pump you hear the prime but after fix no. Silly question do you hear it from the back of truck when running. Trying to see if it is just really quiet now and perhaps a check valve or regulator is flipping out.

---------- Post added at 07:56 AM ---------- Previous post was at 07:53 AM ----------

We know the relay works and disconnecting the evap vent valve is not applicable here.

 

[SunlitComet]

at these point ignore the picture above and use this one.

 

[SunlitComet]

After say a few minutes after being warm or hot it does this correct?

What happens if you start it cold then shut of right away wait say an hour or two with the engine still cold what happens? Was thinking a vapor lock issue but I thought that wasn't really an issue in fuel injection anymore.

 

[BattelWagun]

[/COLOR]So before the pump you hear the prime but after fix no. Silly question do you hear it from the back of truck when running. Trying to see if it is just really quiet now and perhaps a check valve or regulator is flipping out.

e.

Haha yeah true the EVAP wont be much help here...

I used to be able to hear a constant electrical motor whine when the truck was on, now i cant hear anything at all while the engine is running. Also if i start it cold and shut it off quick and come back a while later, no change, its still hard to fire up.

I think I'll just be dropping the tank this weekend...

 

[SunlitComet]

can you get your hands a fuel pressure gauge to do some test?

 

[BattelWagun]

Allright, PROBLEM SOLVED! As I expected, there was a wiring issue. I finally just dropped the tank today (it was a major ***** too may i add) and one of the wires on the connector that hooks up to the pump had broken. I soldered it together and now the pump comes on and stays on until the system is pressurized. It still doesn't quite start the same however... I think i may clean the throttle body next? MAF sensor? I know the injectors are ok, and the fuel system has constant pressure, so I know that issue is all sorted out. Also it looks like A new head gasket/freeze plugs may be in my future too (antifreeze on the transmission), and the ABS light is on... haha It can never be working perfectly fine for more than a day can it?

 

[SunlitComet]

cleaning the maf and tb is always good. If you have not done the fuel filter yet then by all means. I believe the coolant leaks in rear were ussually the intake gasket commonly. I personally after doing a filter would run the pump for a minute or two to flush out any trapped air before starting. Can be done by shorting the power wires on the relay block.

I had one or two days after doing my k&n FIPK where things were great until it went to crap. Hopefully next week can get some money to get a pressure guage for compression and fuel. I have 2 cylinders out and detonation under load, no coss contamination of fluids(yet) and I just did my spider swap less then 300 miles ago back in February. I was so convinced that was it for engine repairs I went on doing electronics, carpets, suspension upgrades and other maintenance.

Is there any recourse for the shop that did the pump in the first place for the time you put into it?

 

[BattelWagun]

Is there any recourse for the shop that did the pump in the first place for the time you put into it?

To tell you the truth, I've tried once already and it didn't work. I'm not going to bother again, we only brought it there beacuse it was the cheapest tow. It wasn't really my choice. my dad still technically owns the truck and I'm letting him because that means I get war veteran plates and Policemans registratons (I.e- no tickets for me! ) Anyways, theres a big language barrier, and like all shops, the minute you tell them check this, or say "hey, i think this is hooked up wrong" they get all pissy. So needless to say, I got nowhere with that....

And now that I think of it, that filter hasnt been done since before i got the truck, si I may try that too.

And I know exactly what you mean sunlitcomet, you think that everything should be fine for at least 6 months, at least! and the BOOM! something completely random strikes... Oh well, the nature of these beasts I guess. People call me crazy for pumping so much cash into my rig, but I'll be happy in 20 years (if it doesnts explode by then) when our trucks become valuable like the old chevy C trucks and ford F pickups.