97 Gmc 1500

LizardofLaw · June 14, 2009

So heres the skinny, was driving to work and it just turned off. I checked the fuel pressure and fuel filter and all is well. So I hook up my innova obd2 reader and it spits out a p0108 "baro to map signal circuit too high" so I figure the map sensor crapped out. I pick up a new one (74.99$ at napa) slap it in and turn it over, no go. now I try dumpin a lil gas down the throttle body and it fires right up, then dies. frustrated by now I reset the ecu and reconnect the scan tool, zero codes now but it flashes the symbols for the catalyst monitor, oxygen sensor monitor, oxygen sensor heater monitor, and the egr monitor, all of which are bran new. Any ideas? my frustration level is at an all time high and help would be great

ZZ327 · June 14, 2009

I would say its the fuel pump, when you said you dumped a little gas in the TB and it fired and died. But you say the fuel pressure is OK??

bill190 · June 14, 2009

Check the battery for a full charge (12 something volts with ignition on) and clean terminals.

Check all fuses...

http://www.dinosaurelectronics.com/Test_Fuse.htm

Check (and maybe also service) the fuel system...

http://www.asashop.org/autoinc/june98/techtotech.htm

green 788 · June 15, 2009

I would say its the fuel pump, when you said you dumped a little gas in the TB and it fired and died. But you say the fuel pressure is OK??

+1 there... it's possible the pump is weak, and not pushing enough pressure to open the injectors.

Can you hear the pump running when you turn the key on? (You won't necessarily hear an aftermarket pump, but the OEM Delphi pump has a distinctive "zinging" sound when it's happy)...

If the engine wants to run when you put fuel in the throttle body, that says bad pump or plugged fuel filter to me...

You'll also have a fuel pump control relay that you may want to check. It's under the hood on the driver's side... there are instructions for troubleshooting that relay in the shop manual (I have a Haynes manual for my truck, and they show it in there). This relay gives the pump a 2 second run when you first turn the key on to get the pressure up to running spec.

Swap out the fuel filter first (you'll need to do that anyway, even if you do replace the pump).

And those trouble codes are oftentimes more "trouble" than they're worth... sending you on a wild goose chase about 2/3's of the time from what I've seen.

I still say nothing beats good old common sense. ;)

Dan

grose67 · June 15, 2009

I would say its the fuel pump, when you said you dumped a little gas in the TB and it fired and died. But you say the fuel pressure is OK??

+1 there... it's possible the pump is weak, and not pushing enough pressure to open the injectors.

Can you hear the pump running when you turn the key on? (You won't necessarily hear an aftermarket pump, but the OEM Delphi pump has a distinctive "zinging" sound when it's happy)...

If the engine wants to run when you put fuel in the throttle body, that says bad pump or plugged fuel filter to me...

You'll also have a fuel pump control relay that you may want to check. It's under the hood on the driver's side... there are instructions for troubleshooting that relay in the shop manual (I have a Haynes manual for my truck, and they show it in there). This relay gives the pump a 2 second run when you first turn the key on to get the pressure up to running spec.

Swap out the fuel filter first (you'll need to do that anyway, even if you do replace the pump).

And those trouble codes are oftentimes more "trouble" than they're worth... sending you on a wild goose chase about 2/3's of the time from what I've seen.

I still say nothing beats good old common sense. ;)

Dan

You need to put a pressure gage on the pump. There should be a schrader valve near the back of the engine

to the right of the distributer as you look at it. If I had to guess, the pump is shot. I have been through this several times. The fun part is jacking the bed up so you get to the pump. Either that or drop the tank.

LizardofLaw · June 17, 2009

ok, I threw the fuel pressure tester on and I get 17-20, my manual is horrible and it seems like I should have more like 50- 55, anyone know if this is true?

grose67 · June 17, 2009

ok, I threw the fuel pressure tester on and I get 17-20, my manual is horrible and it seems like I should have more like 50- 55, anyone know if this is true?

At least that much. I was thinking 60. The pumps shot.

grampadirt · June 17, 2009

ok, I threw the fuel pressure tester on and I get 17-20, my manual is horrible and it seems like I should have more like 50- 55, anyone know if this is true?

At least that much. I was thinking 60. The pumps shot.

+1,not near enough pressure

bill190 · June 17, 2009

Be aware there is also a "fuel pressure regulator" in the scheme of things. Might want to test that as well.

LizardofLaw · June 19, 2009

Thanks to all of you, I thought there was no way it was the pump, I replaced it in oct. 08. I sucked it up and bought a new one for 93 bucks today and KAZAAAAM! runs like a champ! but I am really disappointed in carter fuel pumps now. I cant for the life of me figure out what would waste a carter fuel pump in 8 months (I drive it like 20 miles a week) so maybe one of you "geru's" could think and share on the topic of "how to care for your fuel pump" By the way I am giddy to have my truck stompin fords again thank you all. This was my FIRST time using these forums and they saved me, I WILL STICK AROUND. Maybe some day we can all talk and trouble shoot my 1976 nissan 280 zx that I de-nissaned and stuffed a 1967 chev 327 that I bored out, keith blacked, gear drived, and for the love of holly made pull wheelies.. I thank you all!!!!!!!!!!!!!!!!!!!!!!!

BTW ask me how I can pull my fuel pump in 5 min .... lol never mind I bet you can guess