Low fuel pressure, reg or pump?
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
Low fuel pressure, reg or pump? The car is all tuned no fuel trims. Now running in open loop all the time.
What I have:-
Walbro Fuel Pump about 8000 miles on it.
Wideband AFR guage
Analogue fuel pressure guage on the rails.
Stock fuel pressure regulator.
Car has 124,000 miles on it.
Symptons:-
I am running in open loop all the time, I have made it so on idle I'm at about 15.5:1 AFR. Have no cats to worry about. From cold it runs rich like it should, after sitting in traffic, or after starting the car 20mins after being fully warmed up it could read 16:1 AFR or even worse 17:1 AFR. I looked at my analoguge guage on the rails, I tend to not trust this too much as by pressing the glass I see a different reading. Has read 40 PSI on tick over, when cold its 58PSI.
Yesterday I was driving back not using the accelerator, just low revs at 30mph, was reading 17:1 AFR I would expect 15ish, the car felt very week, so may have been leaner than 17:1 as guage dont go higher. Then suddenly it stared running at 14.6 and got stronger. Its almost as if a blockage had left. I think what really happened I was wunning at 40PSI and it went back to the correct 58PSI.
I beleive I am loosing fuel pressure, I dont think its just a wacky guage as I can see it running leaner during low fuel pressure readings even on idle.
The regulator as far as I know is the standard on from the factory. Do these go duff, when they go duff do they loose pressure.
If its the pump, I havn't gone below 1/4 tank, and today when I lost pressure I have a full tank of gas.
In the short term I can get round this by putting it back in closed loop and let the fuel trims take up the slack. I want to sort the fuel pressure do you think getting a new regulator would solve the problem?
Where is the regulator located? is it at the top of the tank where the fuel pump plumbs into?
What I have:-
Walbro Fuel Pump about 8000 miles on it.
Wideband AFR guage
Analogue fuel pressure guage on the rails.
Stock fuel pressure regulator.
Car has 124,000 miles on it.
Symptons:-
I am running in open loop all the time, I have made it so on idle I'm at about 15.5:1 AFR. Have no cats to worry about. From cold it runs rich like it should, after sitting in traffic, or after starting the car 20mins after being fully warmed up it could read 16:1 AFR or even worse 17:1 AFR. I looked at my analoguge guage on the rails, I tend to not trust this too much as by pressing the glass I see a different reading. Has read 40 PSI on tick over, when cold its 58PSI.
Yesterday I was driving back not using the accelerator, just low revs at 30mph, was reading 17:1 AFR I would expect 15ish, the car felt very week, so may have been leaner than 17:1 as guage dont go higher. Then suddenly it stared running at 14.6 and got stronger. Its almost as if a blockage had left. I think what really happened I was wunning at 40PSI and it went back to the correct 58PSI.
I beleive I am loosing fuel pressure, I dont think its just a wacky guage as I can see it running leaner during low fuel pressure readings even on idle.
The regulator as far as I know is the standard on from the factory. Do these go duff, when they go duff do they loose pressure.
If its the pump, I havn't gone below 1/4 tank, and today when I lost pressure I have a full tank of gas.
In the short term I can get round this by putting it back in closed loop and let the fuel trims take up the slack. I want to sort the fuel pressure do you think getting a new regulator would solve the problem?
Where is the regulator located? is it at the top of the tank where the fuel pump plumbs into?
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
Went out today for a 45 minute drive in each direction, mainly on the freeway, a little round town, never lost any fuel pressure.
I know there is a post about Walbro's dropping out, so many people say they are reliable, people mainly post of problems. My reguilator is old.
What should I check? I guess I'll take a look at the pump in the tank and go from there.
I know there is a post about Walbro's dropping out, so many people say they are reliable, people mainly post of problems. My reguilator is old.
What should I check? I guess I'll take a look at the pump in the tank and go from there.
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
Well drove the car to work this morning, got to work in 10mins, no i wasn't driving fast, I'm just lazy and take the car of instead of the cycle. Got to a stop sign and it was runing pig rich on idle. got to work took a looked at the fuel presure guage it was reading about 67ish.
I guess that points towards the fuel presure regulator now. As low pressure could be either pump or regulator, but high pressure must be the regualtor, right??
Can anyone offer advice on a fuel pressure regulator?, where to get one from, perhaps I could fit a stock one in there, or is there another make which is better but the same price. I may be goiung FI in future, duel pumps etc, dont want to do too much cutting getting a regulator to fit.
I guess that points towards the fuel presure regulator now. As low pressure could be either pump or regulator, but high pressure must be the regualtor, right??
Can anyone offer advice on a fuel pressure regulator?, where to get one from, perhaps I could fit a stock one in there, or is there another make which is better but the same price. I may be goiung FI in future, duel pumps etc, dont want to do too much cutting getting a regulator to fit.
I wouldn't say that its a fuel pressure thing, I'd get a fuel pressure gauge in the car that you can trust and them just read the darn thing... I'd bet it has more to do with the tune.
Ryan K.
Ryan K.
Thread Starter
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
I'm begining to think the fuel pressure guage has be correct all along.
The fuel pressure I'm getting isn't consistant, certainly from old everything is perfect, up to temperatue and sitll perfect, sit in traffic and could still be okay, turn the car off for 10mins, turn it back on, wait a min and then I could have less pressure, it not consistant so as I was having less pressure I assumed the pump, but now I seen high pressure then I think it could be the fuel pressure regulator.
On idle its running good afr, loose pressure it goes lean, increased pressure it goes rich. Running in open loop so O2' s are out of the equation, injector duty cycle is constant at idle, same temperature, I dont beleive it is the tune. I think I should possible try new pressure guage. Would'nt mind a dash oard one, as opening the hood can only really be done when parked, unless i ge tmy mate to look under the hood and tie him in there when do a few WOT runs. lol. I think looking at the fuel pressure guage will be the last thing on his mind.
Has any one got an oil filled guage that when you press on the glass you can vary the reading by 5psi?
The fuel pressure I'm getting isn't consistant, certainly from old everything is perfect, up to temperatue and sitll perfect, sit in traffic and could still be okay, turn the car off for 10mins, turn it back on, wait a min and then I could have less pressure, it not consistant so as I was having less pressure I assumed the pump, but now I seen high pressure then I think it could be the fuel pressure regulator.
On idle its running good afr, loose pressure it goes lean, increased pressure it goes rich. Running in open loop so O2' s are out of the equation, injector duty cycle is constant at idle, same temperature, I dont beleive it is the tune. I think I should possible try new pressure guage. Would'nt mind a dash oard one, as opening the hood can only really be done when parked, unless i ge tmy mate to look under the hood and tie him in there when do a few WOT runs. lol. I think looking at the fuel pressure guage will be the last thing on his mind.
Has any one got an oil filled guage that when you press on the glass you can vary the reading by 5psi?
