Lowering fuel pressure when starting
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Lowering fuel pressure when starting
This is fora 1992 F150, MASS AIr (converted), 351W, EFI
When I try to start my new motor, I am getting a fuel pressure that is at 34 psi. with the key just being on to below 28 when I try to start the motor. As soon as I start it, the pressure lowers one psi at a second until it gets to at least 28. The digital gauge flashes when the pressure goes below 28. The last time I checked there were no codes from the PCM.
Is there a secondary circuit that supplies more power to the system? I am not sure.
When I try to start my new motor, I am getting a fuel pressure that is at 34 psi. with the key just being on to below 28 when I try to start the motor. As soon as I start it, the pressure lowers one psi at a second until it gets to at least 28. The digital gauge flashes when the pressure goes below 28. The last time I checked there were no codes from the PCM.
Is there a secondary circuit that supplies more power to the system? I am not sure.
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The EFI computer has absolutely no control over fuel pressure, your pressure is low.. should be 40psi without engine vacuum, and that's either because of a weak pump, low voltage at the pump, a partially clogged filter, a leaking regulator, or a leak between tanks on dual tank trucks.
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I removed the fuel filter and the gas in there has a yellow tinge to it. The gas is a year and a half old. I put some stabilizer in the tank but it never got in the lines. I'm not sure how much resistance the filter should have but it has some so I'll replace it.
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I believe that the fuel filter was restriced and so was a fuel pump I had mounted on the fuel rail for my supercharger. When I blow through each, there is a good bit of restriction and I don't think it should be that high. Both are probably bad from the fuel.
The fuel pressure regulator and fuel rail seem OK and I think they are. I disconnected them a while ago so the fuel didn't stay in there that long. Besides, the fuel pressure regulator seems to pass the tests I have been doing.
I think I need to replace the in-tank fuel pump next. I bet it is gunked up.
I was also going to test the fuel relay for voltage. Have any idea what I should read from each connection?
The fuel pressure regulator and fuel rail seem OK and I think they are. I disconnected them a while ago so the fuel didn't stay in there that long. Besides, the fuel pressure regulator seems to pass the tests I have been doing.
I think I need to replace the in-tank fuel pump next. I bet it is gunked up.
I was also going to test the fuel relay for voltage. Have any idea what I should read from each connection?
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I replaced the fuel filter and the in-tank pump. When I had the fuel filter installed and the in-tank pump out, I blew through the lines and they seemed to be clear all the way up to the fuel rail. I am getting about 36 psi with KOEO and it doesn't drop nearly as much when I try to start, it stays in the 30s but still not starting.
There were two codes: 21 & 24. From what I found on line, I am not sure they would prevent the motor from starting.
To this point I haven't replace the fuel pressure regulator or the fuel rail and I am using some old, used 19# injectors. The fuel pressure regulator checks out (no leaking fuel past diaphram). I am fairly confident that the fuel rail is clean. I was trying to get it running with the stock injectors just to change as little as possible but now I am thinking I might switch to the new, 30# injectors I have because they are new and clean.
There were two codes: 21 & 24. From what I found on line, I am not sure they would prevent the motor from starting.
To this point I haven't replace the fuel pressure regulator or the fuel rail and I am using some old, used 19# injectors. The fuel pressure regulator checks out (no leaking fuel past diaphram). I am fairly confident that the fuel rail is clean. I was trying to get it running with the stock injectors just to change as little as possible but now I am thinking I might switch to the new, 30# injectors I have because they are new and clean.
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I would keep the 19# injectors in till you get it to run , when you put in the 30# you will need a computer tune or a mass air meter thats set for 30# injectors , with 36 psi it should start then the fuel pressure will come up to around 40-43 , are you sure you have the timing right , TDC on the compression stroke , it could be 180 out ??.....Lew
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I would keep the 19# injectors in till you get it to run , when you put in the 30# you will need a computer tune or a mass air meter thats set for 30# injectors , with 36 psi it should start then the fuel pressure will come up to around 40-43 , are you sure you have the timing right , TDC on the compression stroke , it could be 180 out ??.....Lew
I do have all the calibration needed for the 30# injectors but would still like to get it running with 19# injectors first.
As for the timing, I am getting occasional detonation so I am pretty sure I am on the compression stroke, but wouldn't be too much trouble to change it. When I put the distributor in and the crank is at 0 deg (TDC), the rotor in the distributor is pointing to the right (3 o'clock) when looking from the front to back of the truck. I am looking for a final timing of 14-16 BTDC so I am rotating the distributor a little clockwise and then trying to start the engine.
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From: Calverton
B When I put the distributor in and the crank is at 0 deg (TDC), the rotor in the distributor is pointing to the right (3 o'clock) when looking from the front to back of the truck. I am looking for a final timing of 14-16 BTDC so I am rotating the distributor a little clockwise and then trying to start the engine.
3 o'clock is not correct for #1 @TDC, most likely timing being your problem
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That's not right?
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From: Calverton
As long as you can turn her both ways for adjustment, that would be ok. Usually if #1 is not at the 12:30-1:30 o'clock position, you then would have issues with the loss of adjusting rotation movement, and also the electrical lead becoming to short to reach the connector.
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From: Calverton
Let me ask you this, is your #1 wire on the cap at the factory embossed #1 mark on the top of the cap?
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It is. I can tell you this because I just got the truck running. I ran it for about 5 min and realized that I needed more coolant so I got to go get some.
There was a good amount of smoke coming out of the exhaust. Not sure how long that should last for but everything seemed OK. The oil pressure was normal and it was idling fine at 2300 RPM. No strange bangs or noises. I am just not sure what to expect. It's my first motor I installed, let alone put together. I am surprised I got it to start.