Low speed pump

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giamanut

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Okay I've searched Now heres what I've got.
KOEO in this order
524 low speed fuel pump circuit open(pump runs fine)
543 fuel pump circuit open-Battery to PCM ( pump runs fine)
Running I get these
136 Can't find it anywhere!
172 O2 indicates lean This is possible but I have some black plug after maybe 30mins of running so I'm thinking not.
This car has 2 broken knock sensors However when you pull the shut it should go to 10 degrees BTDC and not accept timing from the PCM It runs the same with or without shunt at idle. I know the knock sensors are bad but the car should idle and it will for a few minutes. That 524 really gets me. I have had the plugs out and they looked golden but the last time I pulled them some where quite black I installed new ones and wires, it would not idle at all before the new plugs and wires. I change 1 O2 sensor but not the other. It is possible the other one is bad and maybe its saying lean when the plugs say I'm black, and can this relate to the 534 code.
So one question I have is can the 524 code be caused by the o2 sensor asking for more fuel at idle which could cause the pump to go to normal speed. I have found this code in searches and have seen the fix be an o2 sensor. This makes sense to me if the low speed is only used at idle.
I'm not sure when the low speed pump circuit is in play does anyone know.
 
Interesting... Im getting a 524 code and a whole mess of O2 codes (175,176,177,181,189) And Im having a problem at wide open throttle so I plan on a tune up to help and a looking at O2's and fuel pump. Did or do you have any problems accelerating also?
 
136 - heated o2 sensor indicates lean left side
172 - heated o2 sensor indicates lean right side

The other codes are history codes. You may have turned power on, and the inertia switch may have been tripped. Or a fuel pump fuse may have been blown. The 2 codes during engine run, are telling you the engine is running lean and the computer cannot compensate enough. You either have a vacuum leak some where, or you have a bad/dirty maf meter. IF you only have 1 or 2 plugs that were black on either side, then I would think you have some very dirty, or stuck open injectors.

Edit: I only see a 542 and 543 codes: no fuel pump power to the pcm and no fuel pump power from the pcm to motor. As I said before, you prolly had a power interuption somewhere between the battery and pcm.

Edit2: IF you have an even number of plugs that are black, you may have 1 or 2 weak coil packs. Check which plugs were black, and then check the coil packs to see if they are linked. If the spark is weak, there may be excess oxygen in the cylinder which is being pumped into the exhaust. The o2 sensor sees this and opens the injectors a little more to compensate.
 
Well thanks guys I know the inertia switch is fine and I have had the battery dis connected a few times still get the 524, but I'm gonna change the passenger side o2 tomorrow before anything else The car had a blown head gasket for a few miles enough of a leak that i could bubble the coolant tank when cold just by cranking the car but it still idled at that point but soon after became hard to start. So I changed the gaskets and thats all good I have kept it running long enough to be sure everything is mechanical okay. But I do wonder about a vac leak I sprayed around with some cleaner and didn't get any indications but I couldn't do a thorough job on that. the 02 sensors might have gotten fouled when the head gaskets where bad. Oh the black plugs where 3-4-7-8 1&2 where getting there and 5&6 where wet. After installed the new plugs and wires there are no misses
just runs rough definitely a mixture issue I'm thinking.

Oh I pulled all my relays in the engine box set my alarm off and cycled them all through the most fwd relay plug and they all blink the lights so all five are good fuel pump horn etc.....
 
Yes I believe the o2 can effect the 524 code It's only a guess but I'm thinking the pwm of the injectors would be out of range at idle at normal pressure so they cut the pressure at idle to keep a usable pwm but once the 02 sensor ask for more fuel IE more pwm the low speed circuit opens to allow normal pressure. This is not facts that I got from ford this is the only reason I could come up with that they would even have a low speed fp circuit.
 
Yeah, a blown head gasket could kill an O2 if enough water got in the exhaust. So replaceing both front O2s is a good idea. But I also would bet you have an intake leak. Did you reuse the old IMRC and plenum gaskets?
 
First of all, there is no such code as 524. It's 542. It deals with battery power going to the fuel pump circuit inside the VCRM. Fuel pressure is controlled by the fuel pressure regulator and is adjusted by vacuum. You should have around 30-32 psi at idle. Under low vacuum conditions, (WOT) it will adjust to 40-42 psi. The fuel injector pulse width is set by the MAF, and adjusted by the o2 sensor. The MKVIII uses Pulse Width Modulation, to reduce fuel pump speed. This intern reduces the amount of fuel being returned to the fuel tank, thus reducing fuel heating, thus reducing fuel vapors. This is your "low speed fuel pump relay". The high speed fuel pump relay is located in your engine compartment fuse box. IT is grounded inside the VCRM upon command from the PCM. It is only used during WOT and when heavy loads are placed on the engine. If your codes 542 and 543 were current faults, the engine would not be running, as there would be no power to the fuel pump circuit.
 
If there is no 524 code why does the list I have from Alldata say the following: 524 Problem in low speed fuel pump circuit.
 
ssmoparviii said:
If there is no 524 code why does the list I have from Alldata say the following: 524 Problem in low speed fuel pump circuit.
Click to expand...
Not sure. Why do Dodge Vipers have a warning sticker that says its better to put small children in the back seat? :lol:
 
Psychostang I did get 542&543 (the car was still running)at one point but also got 524 it does exist it may not mean anything but the list I have shows it as low speed fp circuit open. That being said. And I could be wrong but I am pretty should the MAF does not set injector PWM but rather tells the PCM which cell on the fuel table to go to, the table being pre-programed by RPM vs load the o2 sensors adjust any given cell in that table that is too lean or too rich and the value is used to adjust the PWM of the injectors. As far as the high speed pump circuit only being use at WOT that would mean low speed pump circuit was active at all other times So at say 1500 rpm you should not have less than 12v at the pump is this correct? "The MARK VIII uses PWM to control the fuel pump speed" So If I check the pump voltage with the engine running I will see the voltage go on and off? The Fuel pressure regulator will give you 30 psi to the injectors at a given vacuum and given Fuel pump pressure if you change the fuel pump pressure and not the vacuum the pressure at the injectors will change also. Am I just not understanding what you are saying? I can definitely see the low speed fp circuit only closing at WOT because at that point injector are at max duty cycle and so they may need the additional fuel pressure drop by lowering the voltage to the pump. Last thing The o2 sensors could be fouled do to water I'm not sure it would take very much water I guess it would depend on how old they are, but in any case it was not blowing white smoke.
 
LaserSVT

Did you reuse the old IMRC and plenum gaskets?[/QUOTE said:
No I used new gaskets but a vacuum leak is a possibility. I'm going to clean the MAF first. I will be removing the intake again to replace the knock sensors but really wanted to wait on that. I did spray around the intake while running and it seemed tight but it's a little tough with the engine not idling for long. At one point i got the codes for one bank rich the other bank lean that made me think vacuum leak but that all went away when I changed the plugs and wires.
I will Post the fix when I find it for sure.
Click to expand...
 
Cleaned the map today it helped keep it idling long enough to find the vacuum leaks. so now I will order the knocks and goop the hell out of the intake on assemble. I sure this will cure it they are bad leaks both sides of the intake near the middle.
 
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