Big fuel problems..Need your help guys

[Stangfreak95]

Let me start by saying that the car wasnt acting like that last summer after we put the engine back in with H/C/I. It's in the end of the summer that this problem started. The car always had an unstable idle since the swap but I was expecting this. In the middle of the summer, I decided to put an Accufab adjustable fuel pressure regulator to help me not run lean when I'll be on the nitrous. First it was ok. Suddenly a few weeks/days after, the car was losing fuel pressure bad. Lets say I was setting it at 38psi vacuum on after the start, well after a run at the track, or 15minutes after a little cruise in the neighbourhood, the fuel pressure would be at around 29psi. So I'd raise it to 38psi again then run it and shut it down. Next time I start it, the pressure would be at something like 48-49psi vacuum on again.. So I'd lower it again and the same pattern has happened ever since. So I thought it was a bad afpr. I put the stocker back on, which was working fine before I removed it. Pressure would be at 28psi max and even lower. That sure wasnt normal. So I put the afpr back on and the same thing was happening. So then I thought it was a bad fuel pump. So I installed a 255lph brand new Walbro in there last weekend and same results. Now lets look at my fuel components. I have a fairly new fuel filter, 24pds injectors which have about 500miles max on them, new Accufab regulator, new fuel pump...

I thought that my EEC Tuner was the problem but after trying the J4J1 tune which should make the car run way better (not necesserally stronger), I had the same problems. I'm thinking the problem is not the tune anymore.

From what I know, I have the stock o2 sensors on there which would have about80 000miles. Could this be the problem ? What do you think about it all ?

Sorry for the long post guys but I'm getting a little desperate

Any help would be really appreciated again..

Mario

 

[S/CBlack95GT]

You need to check the fuel pressure with the vacuum line off. The pressure can vary a lot with the line connected.

 

[wytstang]

Yeah I would set it with the vac line off first. I wonder if your MAF is maybe going bad??

 

[Stangfreak95]

Even if I would set it with vacuum off, the fuel pressure would still be all over the place. This might be a better way to set it up, but it's not the problem I'm sure of it. I'll do it anyway just to see.

Mass air flow has about 500miles on it. A Pro-M 80mm calibrated for my 24pds injectors..

 

[Stangfreak95]

TTT please

 

[final5-0]

Let me start by saying that the car wasnt acting like that last summer after we put the engine back in with H/C/I. It's in the end of the summer that this problem started. The car always had an unstable idle since the swap but I was expecting this. In the middle of the summer, I decided to put an Accufab adjustable fuel pressure regulator to help me not run lean when I'll be on the nitrous. First it was ok. Suddenly a few weeks/days after, the car was losing fuel pressure bad. Lets say I was setting it at 38psi vacuum on after the start, well after a run at the track, or 15minutes after a little cruise in the neighbourhood, the fuel pressure would be at around 29psi. So I'd raise it to 38psi again then run it and shut it down. Next time I start it, the pressure would be at something like 48-49psi vacuum on again.. So I'd lower it again and the same pattern has happened ever since. So I thought it was a bad afpr. I put the stocker back on, which was working fine before I removed it. Pressure would be at 28psi max and even lower. That sure wasnt normal. So I put the afpr back on and the same thing was happening. So then I thought it was a bad fuel pump. So I installed a 255lph brand new Walbro in there last weekend and same results. Now lets look at my fuel components. I have a fairly new fuel filter, 24pds injectors which have about 500miles max on them, new Accufab regulator, new fuel pump...

I thought that my EEC Tuner was the problem but after trying the J4J1 tune which should make the car run way better (not necesserally stronger), I had the same problems. I'm thinking the problem is not the tune anymore.

From what I know, I have the stock o2 sensors on there which would have about80 000miles. Could this be the problem ? What do you think about it all ?

Sorry for the long post guys but I'm getting a little desperate

Any help would be really appreciated again..

Mario

Hey Mario

I'm gonna TTT this one for you cause I wanna hear what more of the guys have to say about the fuel pressure not being stable.

I've never looked at fuel pressures but SCBlack95GT says it can vary but ...... can it be THAT MUCH?

I've been thinking about this some today and since you have replaced pump, regulator, & fuel filter I just don't know.

Unless the voltage that feeds the pump is not steady I can't think of anything else.

Come on guys

Lets help Mario and educate Grady all at the same time

Later
Grady

 

[Stangfreak95]

Hey Grady Thanks for bring that up TTT for me. I was just checking the voltage at the fuel pump (actually at the inertia switch) and I got my 12V while the car was running so everything is good there. Then I go under the hood and look down on the passenger side just like that and...WTF there's a plastic vacuum line that melted on my longtubes I had that vacuum leak propably since I took the car out this year...So my problem might be solved...I'll know tomorrow when I drive it and check if the fuel pressure is still all over the place, even after the install of my 255lph fuel pump.

No wonder the s.o.b. was drinking gas some much since I put it back on the road...

 

[loud 95]

As the pump is now new, your fuel sending unit may be bad.

 

[final5-0]

Hey Grady Thanks for bring that up TTT for me. I was just checking the voltage at the fuel pump (actually at the inertia switch) and I got my 12V while the car was running so everything is good there. Then I go under the hood and look down on the passenger side just like that and...WTF there's a plastic vacuum line that melted on my longtubes I had that vacuum leak propably since I took the car out this year...So my problem might be solved...I'll know tomorrow when I drive it and check if the fuel pressure is still all over the place, even after the install of my 255lph fuel pump.

No wonder the s.o.b. was drinking gas some much since I put it back on the road...

You know what Mario

Nit pikin little problems and various issues can jump up after a big motor upgrade like the one you just did and its usually something simple just like what you found.

Stuff like loose or faulty wire connection, vacuum leaks, oil or water leaks and .... well you get the idea.

Sorting out that kind of stuff can drive you crazy and kinda takes the fun out of modding the old Stang

I can see how a serious vacuum leak would hose up the regulator

Glad you found the prob now you can focus on the combo

Later
Grady

 

[Stangfreak95]

You know what Mario

Nit pikin little problems and various issues can jump up after a big motor upgrade like the one you just did and its usually something simple just like what you found.

Stuff like loose or faulty wire connection, vacuum leaks, oil or water leaks and .... well you get the idea.

Sorting out that kind of stuff can drive you crazy and kinda takes the fun out of modding the old Stang

I can see how a serious vacuum leak would hose up the regulator

Glad you found the prob now you can focus on the combo

Later
Grady

Well there's one problem solved Grady..but the fuel pressure is still not "locked" in place. Pisses me off. Anybody else have any ideas ?