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2004 BF150 low fuel pressure

B

Boat dude

New member
I have code 48-5 but I have replaced the air flow sensor with a OEM and it didn’t help. I checked the fuel pressure after the fact and I’m getting 38 PSI pretty consistently. When I disconnect the small vacuum line the pressure jumps up to around 43.

I replaced the pump with a Quantum primarily to test it bc the one in there was OEM and only a year old or so.

I have replaced all 3 filters (water separator in bilge, the cartridge in the small bowl, and the high pressure in the VST housing.

I’m leaning towards fuel pressure regulator bc I’m really not sure what else it could be.

FYI. I did run it on a portable tank and it didn’t change the PSI.
 
What did the screen below the fuel pump look like? Is it idling ok then when you go to run it, it boggs down under a load??
 
If your having trouble getting plastic fuel pump holder/filter screen out, try putting 3 zip ties down it one behind each lock tab and pull it up.
 
HonDan said:
What did the screen below the fuel pump look like? Is it idling ok then when you go to run it, it boggs down under a load??
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Do you think it could be the fuel pressure regulator?

I’ve had issues with fuel pumps over the years on different things but not a regulator that I can remember.

I changed the plugs before I checked the fuel pressure thinking it may help the rough idle.

I can drop a cylinder with my laptop and each one makes a difference.
 
When you say you can drop a cylinder with your laptop are you saying you have a Dr H connected?
I don't think it's the fuel regulator, but there is a regulator discharge test on page 250 in service manual to check it.
It sounds more like a fuel injector.,
Pull each power connector off the injectors one at a time and see which one changes the engine the most or the least. Pulling a good one will make it more bad. The bad/weak injector would be the one that has the least effect on the engine. If you can notice the difference, and identify it try to clean or replace it
If injectors are all the same. It's likely the shaking can be resolved with valve adjustment, worth the effort to pull valve cover and run feeler gauge on them to inspect clearances3-13/p102. 150 should get clearance / adjustment around 600 hours
 
HonDan said:
When you say you can drop a cylinder with your laptop are you saying you have a Dr H connected?
I don't think it's the fuel regulator, but there is a regulator discharge test on page 250 in service manual to check it.
It sounds more like a fuel injector.,
Pull each power connector off the injectors one at a time and see which one changes the engine the most or the least. Pulling a good one will make it more bad. The bad/weak injector would be the one that has the least effect on the engine. If you can notice the difference, and identify it try to clean or replace it
If injectors are all the same. It's likely the shaking can be resolved with valve adjustment, worth the effort to pull valve cover and run feeler gauge on them to inspect clearances3-13/p102. 150 should get clearance / adjustment around 600 hours
Click to expand...
I have the Texa marine software. I can kill a cylinder separately.

The engine has about 300 hours total on it.

Would the 38psi not worry you?

I did the regulator test by the book and it seemed fine. It jumped about 5 psi with the small vacuum line off and pinched.

I’ll test it later this week by pulling the injector plugs.
 
Boat dude said:
I have the Texa marine software. I can kill a cylinder separately.

The engine has about 300 hours total on it.

Would the 38psi not worry you?

I did the regulator test by the book and it seemed fine. It jumped about 5 psi with the small vacuum line off and pinched.

I’ll test it later this week by pulling the injector plugs.
Click to expand...

HonDan said:
If after you check injectors, did you already check and clean idle air control valve?
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I have not pulled it to clean just bc it doesn’t sound right even with some throttle.
 
HonDan said:
There is another regulator flow test that tests amount of fuel flow in two seconds.
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Yes I did that using my wife’s glass kitchen measuring cup. She wasn’t happy lol.

I had to do it twice to get it up to the first measuring mark. I’ll try that again. After 2 key in switches it was with in the parameter. I can’t remember what it was or what it was supposed to be though. It was with in the specs.
 
I just looked up Code 48-5. Ref page 5-15 p169 It is O2 air fuel sensor code not an air flow sensor that you replaced. Look at other posts on this site for 150 02 sensor. Can ohms check it, can clean it with carb cleaner and brass wire wheel. But if heater sensor is out you will need to replace it. Can get the Walker o2 sensor for less then denso.
 
HonDan said:
I just looked up Code 48-5. Ref page 5-15 p169 It is O2 air fuel sensor code not an air flow sensor that you replaced. Look at other posts on this site for 150 02 sensor. Can ohms check it, can clean it with carb cleaner and brass wire wheel. But if heater sensor is out you will need to replace it. Can get the Walker o2 sensor for less then denso.
Click to expand...
Sorry I either typed in flow or misspelled and it changed to flow. But I did change the fuel sensor/oxygen sensor. The one that screws into the top of the exhaust. I checked the resistance and it was slightly low then I drove it and the code came up after a while of driving. Then I changed it.

AI google is mentioning a relay???? I haven’t looked but it will be a few days before I get back to it.

I have a friend that has an injector cleaning/tester table top deal. I thought about pulling the fuel rail and having him just check them all to check pattern and volume?
 
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