Running really rich

[Bugga390]

Hi guys i have a 1986 ford ranger 2.9 2wd 5 speed, the truck runs super rich and does not want to idle, the map sensor signal stays at 2.6 volts all the time i have replaced the map sensor and eec with no change any help would be greatly appreciated

 

[rusty ol ranger]

Hi guys i have a 1986 ford ranger 2.9 2wd 5 speed, the truck runs super rich and does not want to idle, the map sensor signal stays at 2.6 volts all the time i have replaced the map sensor and eec with no change any help would be greatly appreciated

Pull the vaccum line off the fuel pressure regulator, see if its got fuel in it.

If it does tht FPR is shot. Pretty common thing.

 

[Bugga390]

I checked the vacuum on fpr not fuel coming out im getting 5 codes 12,25,33,42,77 i dont want to start throwing parts at it because i know when you have multiple codes alot of time something else is the cause for it

 

[rusty ol ranger]

I checked the vacuum on fpr not fuel coming out im getting 5 codes 12,25,33,42,77 i dont want to start throwing parts at it because i know when you have multiple codes alot of time something else is the cause for it

12 is IAC...wont cause rich
25 is knock sensor (ignore)
77 Is goose test not performed.

33 is EGR valve not opening. 42 is system rich.

First thing i would do is pull the EGR and see if the passages are plugged and make sure the valve is opening and closing.

 

[Bugga390]

Ok i will try that see what it looks like thanks

 

[Bugga390]

Finally got around to checking my EGR valve. The EGR valve is clean and working. The passageways were clean. I replaced the vacuum switch on the intervener for the EGR now the EGR system is working and the code is gone but still running really Rich. I replaced the O2 sensor no change still running really Rich. I have a new EEC and a new map sensor, but my map sensor signal stays at 2.5 V whether I put vacuum on it or not.

 

[rusty ol ranger]

Finally got around to checking my EGR valve. The EGR valve is clean and working. The passageways were clean. I replaced the vacuum switch on the intervener for the EGR now the EGR system is working and the code is gone but still running really Rich. I replaced the O2 sensor no change still running really Rich. I have a new EEC and a new map sensor, but my map sensor signal stays at 2.5 V whether I put vacuum on it or not.

You cant use voltage to test the MAP. It reads hertz IIRC.

Is lt rich cold, warm, or both?

 

[Bugga390]

Its rich on both cold and warm run decent at higher rpm but idle to half throttle its bad so rich its pretty much un drivable

 

[SenorNoob]

Check fuel pressure? Can also tell if you have a leaking fuel system that way.

 

[rusty ol ranger]

Its rich on both cold and warm run decent at higher rpm but idle to half throttle its bad so rich its pretty much un drivable

Hmm....

If it does it at all temps its likely not the O2...those only matter once its warm.

You could check fuel pressure...it would tell you if an injector is hung open....but i think to make it run that bad you would have to have mutiples failed which is unlikely.

It might be worth tossing a regulator on it and trying it. I know on my bronco the regulator was shot and it didnt have fuel in the vaccuum hose like what normally happens.

 

[SenorNoob]

I know on my bronco the regulator was shot and it didnt have fuel in the vaccuum hose like what normally happens.

So letting the fuel pump build all the pressure it could? Or just higher than normal? Either way an oddity for sure.

 

[rusty ol ranger]

So letting the fuel pump build all the pressure it could? Or just higher than normal? Either way an oddity for sure.

No idea. It was smoking and smelled like raw fuel and would barely run. It was my initial thought untill i seen no fuel in the line. Then i kind of ran out of options so i replaced it and it straightend right out.

 

[Bugga390]

Ok so this morning i put my fuel pressure gauge on and key on engine off i have 35 psi at idle i have 30 psi and at around 1500-1800 rpm i have 27 psi i picked up a new multimeter with hertz setting key on engine off the map signal is zero and does not change with vacuum.

When I bought the truck three years ago, somebody had already wired the fuel pump to run constant. It ran OK but has always been a little Rich. I replaced the fuel injectors due to a long hot start. That’s when my really rich condition started. I don’t think it’s the new injectors. I think it was that the Plenum gaskets were leaking and sucking extra air.

 

[rusty ol ranger]

Those pressure readings are a bit on the low side actually. Its usually up around 40koeo and 32ish running.

The plenium is kind of a bitch to get sealed. Theres actually torque specs and a sequence to it that if you dont follow it will leak.

The pump running all the time shouldnt cause rich....any excess just gets blown back through the return line.

Im not sure exactly what the MAP should read but if its not responding to vaccuum it very well could be the issue.

 

[Bugga390]

Im thinking about getting another new set of plenum gaskets and pressure test my old injector and clean them and throw them back in just to see if tjat changes anything