Strange fuel delivery problem

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09-30-2002, 02:05 PM

MIGHTYMOUSE

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Re: Strange fuel delivery problem

thats a wierd one.. there is no electrical connection to the fuel pressure regulator at all.. but i also don't see how running it dry would kill the regulator, but its possible ..
try a new regulator??

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10-01-2002, 12:27 AM

1 Bad Z

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Strange fuel delivery problem

Ran my car out of gas the other day. I filled it back up with 5 gallons of fuel and it restarted but only with 12psi of fuel pressure. I decided to change the pump and installed the Walbro intank upgrade pump. Started it back up and same problem, 12 psi of fuel pressure. Checked it with a Tech 2 and I am getting a repeated code of P0748
Pressure control solenoid circuit-electrical. I cant find it anywhere in the service manuals. Has anyone ever heard of this. Is it the MAP sensor looking part on top of the fuel sending unit? I understand that controls the pressure in the tank and tells the canister when to purge but why no fuel pressure???

Thanks, Mike.

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10-01-2002, 08:45 PM

1 Bad Z

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Re: Strange fuel delivery problem

No ideas?? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

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10-02-2002, 01:36 PM

Zed_six

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Re: Strange fuel delivery problem

Hopefully you are verifying fuel pressure with a gauge installed on the end of the rail. And a guage that works...eg verified on another vehicle that it's working properly.

At any rate, drop the tank and see if the line is blocked by detaching the shrader valve and blowing compressed air.

Also, check your fuel filter...after 30,000 miles it should be changed anyhoot.

The regulator found at the intake manifold could be faulty but that's very unlikely. Doing a quick swap with a known good unit will tell the tale. And that goes same with what maybe a pressure transducer located at the pump. Whenever I have a fuel issue, I bolt the entire assembly to the tank (w/fuel) and listen for any unusually loud buzzing sounds from the pump (indicating a blocked line or failing fuel pump).
Also, you may want to connect a hose to the end of the fuel rail (schrader valve removed) and note how much time in minutes and seconds it takes to fill 1 gallon or 5 liters of gas. Do the same and compare to similar vehicle to help verify fuel line blockage and pump performance. I think the Walbro 340 (the bigger of the two) is rated at 190 to 220 liters/hour...but check the www for exact specs. Since the fuel goes all the way thru a 3/8" fuel line, expect your values to be 95% of the rated pump output.

Hope that helps,

Chris

<blockquote>quote:<hr />Originally posted by 1 Bad Z:
Ran my car out of gas the other day. I filled it back up with 5 gallons of fuel and it restarted but only with 12psi of fuel pressure. I decided to change the pump and installed the Walbro intank upgrade pump. Started it back up and same problem, 12 psi of fuel pressure. Checked it with a Tech 2 and I am getting a repeated code of P0748
Pressure control solenoid circuit-electrical. I cant find it anywhere in the service manuals. Has anyone ever heard of this. Is it the MAP sensor looking part on top of the fuel sending unit? I understand that controls the pressure in the tank and tells the canister when to purge but why no fuel pressure???

Thanks, Mike.<hr /></blockquote>

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10-02-2002, 08:11 PM

Chris99WS6PWTMET

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Re: Strange fuel delivery problem

1 Bad Z,

I have no ideas to offer on the fuel pressure problem but I can tell you that code P0748 is a tranny code not engine fuel system. P0748 is the code my car kept setting after installing a tranny with a vacuum modulator in it. After trying different resistors to simulate the stock 3-5 Ohms of the stock pressure control solenoid with no luck, we ended up jumpering a PCS in line by the PCM. That cured the code. Are you by chance running a vacuum modulated tranny?

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10-02-2002, 11:56 PM

1 Bad Z

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Re: Strange fuel delivery problem

<blockquote>quote:<hr />Originally posted by Zed_six:
Hopefully you are verifying fuel pressure with a gauge installed on the end of the rail. And a guage that works...eg verified on another vehicle that it's working properly. <blockquote>quote:<hr /> <hr /></blockquote>I've already done that 12-15psi...

<blockquote>quote:<hr /> <hr /></blockquote>At any rate, drop the tank and see if the line is blocked by detaching the shrader valve and blowing compressed air. <blockquote>quote:<hr /> <hr /></blockquote>Which line? the feed or return?

<blockquote>quote:<hr /> <hr /></blockquote>Also, check your fuel filter...after 30,000 miles it should be changed anyhoot. <blockquote>quote:<hr /> <hr /></blockquote>Did that....

<blockquote>quote:<hr /> <hr /></blockquote>The regulator found at the intake manifold could be faulty but that's very unlikely. Doing a quick swap with a known good unit will tell the tale. And that goes same with what maybe a pressure transducer located at the pump. Whenever I have a fuel issue, I bolt the entire assembly to the tank (w/fuel) and listen for any unusually loud buzzing sounds from the pump (indicating a blocked line or failing fuel pump).
Also, you may want to connect a hose to the end of the fuel rail (schrader valve removed) and note how much time in minutes and seconds it takes to fill 1 gallon or 5 liters of gas. Do the same and compare to similar vehicle to help verify fuel line blockage and pump performance. I think the Walbro 340 (the bigger of the two) is rated at 190 to 220 liters/hour...but check the www for exact specs. Since the fuel goes all the way thru a 3/8" fuel line, expect your values to be 95% of the rated pump output. <blockquote>quote:<hr /> <hr /></blockquote>I've got the Walbro 340. Brand new.

Hope that helps,

Chris

<blockquote>quote:<hr />Originally posted by 1 Bad Z:
Ran my car out of gas the other day. I filled it back up with 5 gallons of fuel and it restarted but only with 12psi of fuel pressure. I decided to change the pump and installed the Walbro intank upgrade pump. Started it back up and same problem, 12 psi of fuel pressure. Checked it with a Tech 2 and I am getting a repeated code of P0748
Pressure control solenoid circuit-electrical. I cant find it anywhere in the service manuals. Has anyone ever heard of this. Is it the MAP sensor looking part on top of the fuel sending unit? I understand that controls the pressure in the tank and tells the canister when to purge but why no fuel pressure???

Thanks, Mike.<hr /></blockquote><hr /></blockquote>

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10-02-2002, 11:58 PM

1 Bad Z

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Re: Strange fuel delivery problem

<blockquote>quote:<hr />Originally posted by Chris99WS6PWTMET:
1 Bad Z,

I have no ideas to offer on the fuel pressure problem but I can tell you that code P0748 is a tranny code not engine fuel system. P0748 is the code my car kept setting after installing a tranny with a vacuum modulator in it. After trying different resistors to simulate the stock 3-5 Ohms of the stock pressure control solenoid with no luck, we ended up jumpering a PCS in line by the PCM. That cured the code. Are you by chance running a vacuum modulated tranny?<hr /></blockquote>Not running a vacuum modulated tranny but, I did increase my line pressure using LS1 Edit. I guess that explains that.

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Strange fuel delivery problem

Strange fuel delivery problem

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