airtex fuel pump 99 yukon

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hshark

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so ran across this issue at autozone. My friend is having issues with his 99 yukon and I think its the fuel pump. He had it replaced a couple weeks ago but he purchased a fuel pump from autozone. He just picked one of the two offered. One had code GFU the other has code GFV. What does this all mean? The pump he had was aftermarket so no markings of GFV or GFU. Where can we locate this info? Thanks!
 

lesterl

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One could be 2 connectors, the other 1 connector (electrical), could have different sound insulations in the 2 modules, could be some extra screening, etc..... IDK I guess is the answer.
 

hshark

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the specs are different but I cannot locate any code that is specific on which one his yukon needs. It is missfiring and stalling on stop and acceleration. And it turns off on occasions. I am sure I can call the dealer and ask, but I am sure someone here has come across this issue before. I am almost sure he has the wrong pump GFV. According to 1aauto.com the pump they have when 8th digit vin R is pump GFU. I would just like to find a marking so I can have concrete evidence...
 

lesterl

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I'm shure if he installed an Airtex that aint good news.... As long as your pump developes the proper pressure it should run.....
 

hshark

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yeah it runs, but it missfires when your at a t-light and tap on the gas. It idles up and down and takes off by itself. MAP, MAF, sensors are all (check engine) on aswell. There has to be issues that can arise if you use the wrong pump. If it has pressure it will turn on and run, but I believe other issues can occur. I just don't have the evidence to back up my theory. What will probably end up happening is dropping the tank and getting the proper pump.
 

lesterl

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Check your fuel pressure. The FPR in the intake will regulate out the difference and then it wont matter.

I dont understand "MAP, MAF, sensors are all (check engine) on aswell."
 

hshark

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what I meant by that is that these three sensors are coming up on my obd scanner. I've replaced all three sensors(new) and they still show as being faulty. My hypothesis is they are getting the wrong signals or pressures if you will from the fuel pump that doesnt belong and triggering them to malfunction or possibly maybe a bad engine computer. I just find it funny that 2 fuel pumps are offered there has to be issues if the wrong fuel pump is installed. It's like a chain reaction one thing triggers another. What are your thoughts?
 

lesterl

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Yeah, I think you have other problems..... What values are you getting on your scanner for MAP and MAF?
 

hshark

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I dont have that answer at the moment, but I can tell you proper voltage readings are being sent to them. I was thinking of swapping out the computer....
 

lesterl

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proper voltage readings? How did you check that?
 

lesterl

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We cant see the scanner, what is "proper voltage"?
 

lesterl

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Did you check fuel pressure readings? Has a tuneup been done on it recently? MAF been cleaned/ checked? If you have a scanner, what does it show when acting up?
 

bubinga

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Flint,Mi--------------- 99 Tahoe 2 door LS 5.7
so ran across this issue at autozone. My friend is having issues with his 99 yukon and I think its the fuel pump. He had it replaced a couple weeks ago but he purchased a fuel pump from autozone. He just picked one of the two offered. One had code GFU the other has code GFV. What does this all mean? The pump he had was aftermarket so no markings of GFV or GFU. Where can we locate this info? Thanks!

I'm not sure exactly the differences in the pumps, but they are different, if the old one was GFU or GFL or what ever, thats what U need
 

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hshark

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proper voltage for map is 5v I've done all tune up service. Spark plugs, wires, cap etc. Map, Maf, Iac, have all been replaced. What seems funny to me is they still show up as trouble codes on the scanner. So I replaced the sensors and I still get the cheeck engine light and they come up on the scanner. I m stating to think it is an ECM issue. The pump when checked for pressure was giving good pressure in fact I can press on the fuel lines running into the intake and it squirts plenty of fuel. I am thinking of ordering an ECM of ebay that accoring to the seller is programed to my vin and with GM updates. I am leaning towards the ECM because the trouble codes still come up after sensors have been replaced. If i clear them the yukon runs fine until they come up again within a couple of hours
 

lesterl

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Proper "SUPPLY VOLTAGE" for MAP is 5vdc, if you are reading 5vdc signal, the MAP is reading full scale one way or the other, the MAP will output a signal proportional to the engine vacume.... Should be similar to all sensors, they wont read full voltage unless the engine isnt running. Also the MAF reads out a frequency and not a voltage.

With alot of unrelated errors it could possibly be the ECM, could also be a bad ground, but ECM is a possibility......
 

hshark

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yeah that will be my last plan of attack, if that doesnt fix it I will sell the POS. I am frustrated and this is my last effort to make her run. I am leaning towards the ecm because of the trouble codes still dispaying after I changed everything out. I also thought about bad grounds but didnt and dont know where to start....
 
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