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Author Topic: Could this be a fuel pump problem? Please help!  (Read 2184 times)

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SwampTGP

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Could this be a fuel pump problem? Please help!
« on: August 05, 2013, 04:34:03 AM »

I've posted here a few times about my car.   I have a 1990 McLaren 3.1 motor with a slightly beefier cam and a T3 turbo installed in a different vehicle.   The motor was rebuilt along with the transmission and mechanically both the motor and the transmission are great.  The transmission has a shift kit with a 2800 stall converter and a final gear ratio of 3.73:1.   The ECM was tuned by getting data logs and having a chip made for the car by a gentleman here on this forum who he has been very helpful and patient with me.   My car wouldn't be running without his help. 

The problem is the air fuel mixture.   At idle it's good, under boost it's always perfect, but when you first step on the gas it flat-lines and goes lean reading 000 on the gauge.  The shop that has been tuning this car, as well as PCMForLess (who would not make a chip for me)  has told me that it should be ok to drive the car lean as long as it's not under boost.  For the most part it runs really well, I will lightly step on the gas and as it gets going the air fuel mixture goes up. But it seems if I step on the gas other than feathering it, or if I have been driving it a lot and it's hot out, it will go to 000 and the car will bog down, creeping forward really slow and eventually taking off.  No backfire or anything that would tell me it's an ignition problem (the coils are new with new plugs and wires.)  Once it's off and running, the mixture is great and this car runs like crazy.  It's just when you first step on the gas.  The shop that works on it referred to this as "tip-in."  So, 2 chips have been made from data logs hoping to address this issue but the car is still having this problem and I'm wondering if it's a mechanical problem and not ECM related?   

Could it be the fuel pump?  The pump is the standard GM in-tank used with the original 2.8 normally aspirated motor that came in this car.  The fuel filter has been changed as of when all of this tuning started.  The fuel injectors are 24lb injectors.  Tried bigger ones and tried smaller ones and 24lb was what the car seemed happiest with.   

Thanks in advance for any help the anyone could give me.   This is really frustrating.
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GPChief

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Re: Could this be a fuel pump problem? Please help!
« Reply #1 on: August 05, 2013, 08:20:04 AM »

What is your fuel pressure at idle?  If you search on here you will find what it should be.  Might be your fuel pressure regulator.

I'd also look at your 02 sensor and consider getting a heated (3 wire one) installed.

Are all of your sensors working correctly?  IAC, TPS, MAP?


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2004 GTP -  3.8 Blown - Only modding for MPG.
1997 GTP  - 3.8 Blown - Too many mods to list.
1996 GTP - 3.4 DOHC - Twin to my 1997.
1995 SE - soon to be a 3.8 turbo car.
1990 TSTE x 2 white cloth
1990 TSTE x 1 maroon leather
1990 TGP - 5 speed.

flybynite

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Re: Could this be a fuel pump problem? Please help!
« Reply #2 on: August 05, 2013, 09:10:03 AM »

Sounds to me that the AE vs delta TPS still needs work. I know my service has been slow this year but I'm going to need more than 3 attempts to get it within limits. You should have an extra chip send it my way and I can make the necessary changes and we'll give it another try. I will be in the states the rest of the year so my service should be far better than earlier this year.
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1989 TGP Pace Car
1990 TGP Red/Tan Leather

SwampTGP

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Re: Could this be a fuel pump problem? Please help!
« Reply #3 on: August 05, 2013, 04:22:37 PM »

Thanks flybynite.   No complaints here bud, you've helped me out tremendously and I'm very thankful.  Yeah, Mark said we could get new data logs if you want to go another round with it.  I just felt like I was being a pain in the rear.   So, yes, thank you, I'll send you the one we just took off.         I hate to ask, could you send me your address please?  sorry...

GPChief,  I know the fuel pressure was tested and it was good.   I don't know what the numbers are though.   I did take the fuel pressure regulator apart and cleaned it (can't remember if I was able to find a rebuild kit or not)  I think they wanted an insane amount of money for the entire assembly including the fuel rails because they don't sell the regulator alone. So I just took the one on there apart and cleaned it.    I believe the 02 sensor is heated..  I know I had to replace the el-cheap-o gauge for one that was actually accurate for the data logs.    And all other sensors were replaced with new GM ones from the dealership when I did the rebuild. 

I am concerned about the fuel pump though.  From what I have been told, the TGPs had a Corvette pump in it.  Is that correct?   Would a Wallboro pump be ok?  (I've had bad luck with Wallboro pumps on my Firehawk and went to an Aeromotive pump).     The pump in the car is maybe about 6 years old.  It was the last thing my dad had replaced before they gave up on the vehicle and bought a new one. 
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GPChief

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Re: Could this be a fuel pump problem? Please help!
« Reply #4 on: August 05, 2013, 11:40:07 PM »

I've had luck with the Walbros.  Just put one in my 1990, I increased the wire size & soldered all the connections. 

I had a wiring issue with one, maybe check voltage?  Kind of a PITA since you'll need to drop the tank.

I'll defer to whatever Adam says, he does this for a living :icon_cool:
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2004 GTP -  3.8 Blown - Only modding for MPG.
1997 GTP  - 3.8 Blown - Too many mods to list.
1996 GTP - 3.4 DOHC - Twin to my 1997.
1995 SE - soon to be a 3.8 turbo car.
1990 TSTE x 2 white cloth
1990 TSTE x 1 maroon leather
1990 TGP - 5 speed.

SwampTGP

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Re: Could this be a fuel pump problem? Please help!
« Reply #5 on: August 06, 2013, 07:01:58 PM »

For sure, Adam's been great.  This car was just stumbling all over the place before I found him.  It wasn't even remotely reliable or driveable. 

@ Adam,  I'll text you as well, but here's the whole scoop.   Mark would like to change the plugs to iridium plugs and gap them down a bit first and also use better plug wires and route them properly instead of that giant knot that GM made with them up front by the exhaust manifold.   Then he'll get fresh data logs and get those to you..    So it might be a few days before I get the chip and the logs to you.    Thanks bud..

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