Code 41 and 42 fuel pressure codes

[jaywish]

Hi,
I got the check engine light occasionally yesterday and this morning. So I hook up the reader. Get Keyoff code 41 and Keyon code 42. The reader tells me that both codes are fuel pressure out of range. So I get the pressure gauge. It shows 32 PSI. After shutoff it takes about 20 seconds to drop to 30. I look in Chiltons and it specifies 39PSI for the 5.0 both HO and lopo.

First off as I do not always trust Chiltons is the correct pressure 39PSI?

I have a one year old Spectra tank with a 190LPH Airtex pump. The filter has about 12,000 miles on it.

If the correct pressure is 39 what next?
Filter?
Regulator?

Thanks,
Jay

[gadget73]

These cars have no fuel pressure sensor, so those aren't what the codes are. 41 is lean, 42 is rich, but I don't know which bank thats for. If you're getting both, something is really wonky. If thats a stored code, it means one of the sensors is not switching, and may indicate a faulty O2 sensor or wiring. I want to say the 40 codes are bank one and the 90 codes are bank 2. Bank 1 should be cyls 1-4, bank 2 would be 5-8.

[jaywish]

I told the otc reader that the car was an 89 mark VII. Shouldn't matter? 41 is koeo 42 is koer (darn edit timeouts)

correct fuel pressure?

[jaywish]

Reran test as regular lopo gm.
no koeo codes
koer code 42 is now described as "System Rich"

idle fuel pressure now steady at 31lbs

[Lincolnmania]

o2 sensor issue......maybe a burned or broken wire?

[jaywish]

Will check the wires.

Is 31/32 psi correct at idle?

Couldn't find in the manual where the codes are that define the bank for the rich condition. Is it 1-4 the 40 series codes as Gadget remembers?

[gadget73]

32 psi with the vacuum line connected at idle sounds right. Should be about 40 if you pull the line to the regulator.

If its rich on one side, and it doesn't give you a 44 or 94 and the smog stuff is all present, likely the oxy sensor is working. Check the plugs to see if one looks different. Its possible you have a sticky fuel injector or something on that bank. May also be the sensor is lying but if it passes the thermactor test nonsense, that proves it can register a lean-out condition.

[jaywish]

Just a 42 now. Might be able to get the 41 back if I rode the highway. So is a 4x code the right side?

[gadget73]

I think so. I can't remember for sure though. Where the hell is John, he's the keeper of this information now.

[jaywish]

I will try and spend some more time getting cozy with the manuals. I know they are in one of them somewhere.

[jaywish]

What do you know, When I reread the site sticky it made more sense, once I used the correct vehicle for the reader.

Still not complete sense to me. Is this saying two slightly different things?

42) HEGO circuit indicates system rich (right HEGO) (R)
No HEGO switch detected - always rich (right HEGO) (C)

Jay

[jaywish]

Well here is a picture of the after.



Right Bank Wire connector.
(just in place for the pic, not the final location)

Thanks Guys,

Learned that even with a pcm swap to a lincoln computer still must ID the vehicle as a lopo for correct error code testing.

[gadget73]

well, they're kind of both the same thing. Not switching just means that its not going back and forth from lean to rich. Oxygen sensors, at least the narrow band ones we use, don't so much indicate stoich as they flip fairly rapidly from lean to rich a CH either side of the stoich point. The ECM tweaks the injector pulse back and forth to keep it switching back and forth so it knows its where it belongs. When it doesn't switch, it can be either rich or lean. In this case, its stuck rich.




think of it as a digital device, its either rich or lean, its never actually at stoich. The ECM can't really tell how rich or how lean it is, just that its one or the other. The only way to get a really accurate reading is to use a wideband sensor, but those have a very different voltage curve and the ECM's inputs won't deal with it. I seem to remember John telling me that to use a wideband with an EEC-IV, you give up the EGR sensor or something because thats the only available sensor input that can deal with the range of voltage a wideband outputs.

[jaywish]

That is clear.