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Old 08-26-2010, 04:36 PM
thosfsull thosfsull is offline
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1998 4.6 fuel Pressure Issues

Yes, this is for a 1998 Lincoln with a 4.6L V8. The fuel pressure is much lower than what it should be by half or a third. 2 cylinders once the plug was pulled were gasoline soaked. The more my friend attempts to fix it at his body shop, the result stays the same or worse. He did a compression test and all are 125 plus in the cylinders. He guesses that the fuel pressure is low so the less atomization happens and it puddles in certain cylinders and now all after cleaning the filter.

Any ideas?
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Old 08-26-2010, 06:37 PM
Nightmare97 Nightmare97 is offline
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Originally Posted by thosfsull View Post
He guesses that the fuel pressure is low so the less atomization happens and it puddles in certain cylinders and now all after cleaning the filter.

Any ideas?
I'm thinking that's a pretty bad guess, and what does "and now all after cleaning the filter" mean? Maybe you should do a leakdown test on the injectors, it sounds like some of them are dumping fuel, leaking, stuck open, what-ever. That might explain the low pressure.
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Old 08-27-2010, 07:51 AM
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Johnny Langton Johnny Langton is offline
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What is the fuel pressure KOEO, and KOER, and KOER with the vacuum source removed from the regulator? This is what you need to know.
JL
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Old 08-27-2010, 09:19 PM
thosfsull thosfsull is offline
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Here I talked more in depth with my friend.

Recommended fuel pressure id 55 to 85lbs. Vehicle has 32 lbs.

The car came in with a miss. Pulled the plugs and did a compression test. All were around 125 at each cylinder. Plugs were wet. he checked the fuel pressure at that time and it was about 40lbs but the gauge was jumping back and forth. He put a fuel pressure regulator in and it balanced at 32lbs with the #4 & 8 plugs being wet. Replaced these two injectors. Since then he pulled the plugs again and now all are wet. He believes it is the fuel pump?
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Old 08-27-2010, 09:52 PM
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Quote:
Originally Posted by thosfsull View Post
Here I talked more in depth with my friend.

Recommended fuel pressure id 55 to 85lbs. Vehicle has 32 lbs.

The car came in with a miss. Pulled the plugs and did a compression test. All were around 125 at each cylinder. Plugs were wet. he checked the fuel pressure at that time and it was about 40lbs but the gauge was jumping back and forth. He put a fuel pressure regulator in and it balanced at 32lbs with the #4 & 8 plugs being wet. Replaced these two injectors. Since then he pulled the plugs again and now all are wet. He believes it is the fuel pump?
Fuel pressure spec for an '98 F150 is 40 PSI with the vacuum source removed from the regulator. With the vacuum source attached, it will be lower and will vary depending on vacuum at the time. More engine vacuum=lower pressure.
JL
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2001 F150 Supercab 4.6L/4R70W/3.55
1997 Thunderbird LX 4.6L/4R70W 12.16@111.78
2010 Lincoln MKT Elite-3.5L EcoBoost/AWD 14.41@96.27
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Old 08-28-2010, 02:39 AM
Nightmare97 Nightmare97 is offline
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Quote:
Originally Posted by thosfsull View Post
Here I talked more in depth with my friend.

Recommended fuel pressure id 55 to 85lbs. Vehicle has 32 lbs.

The car came in with a miss. Pulled the plugs and did a compression test. All were around 125 at each cylinder. Plugs were wet. he checked the fuel pressure at that time and it was about 40lbs but the gauge was jumping back and forth. He put a fuel pressure regulator in and it balanced at 32lbs with the #4 & 8 plugs being wet. Replaced these two injectors. Since then he pulled the plugs again and now all are wet. He believes it is the fuel pump?
Plugs don't foul from lack of fuel, it's just that simple. Your friend is pissing in the wind.
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Old 08-28-2010, 08:10 PM
thosfsull thosfsull is offline
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No, I didn't explain it well enough. I believe what he is trying to say is that the plug cylinders are filling or puddling with fuel. Almost like the pressure loss or whatever is causing is screwing up any chance of atomization. I believe it is running too rich as well.
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Old 08-29-2010, 12:07 PM
Nightmare97 Nightmare97 is offline
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Originally Posted by thosfsull View Post
No, I didn't explain it well enough. I believe what he is trying to say is that the plug cylinders are filling or puddling with fuel. Almost like the pressure loss or whatever is causing is screwing up any chance of atomization. I believe it is running too rich as well.
Your friend is reading way to deep, he's letting the electronics scare him. He needs to stick with the K.I.S.S. principle (keep it simple stupid) If he has good spark and all eight plugs are wet, it's possible he has bad gas, water in the tank. These things happen and he needs to check it. Run some fuel into a clear bottle and see if water is at the bottom, gas floats on water.
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Old 08-29-2010, 12:07 PM
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1997, 1998, 46, 46l, 54l, correct, engine, expedition, f150, f250, ford, fuel, lacks, pressure, spec

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