Stalling While Driving/no start

[shr3dd3r 09]

Yes there are 6 wires. There is high resistance between this wire and the battery ground, but I can find nowhere in the wiring diagrams where this signal return wire is grounded...Unless the PCM grounds this wire through another pin. There is also a resistance reading between this wire and the PCM chassis ground, though it is extremely high. Again I can find no evidence to suggest that this wire is grounded anywhere, yet it is indeed connect to two separate grounds, though the resistances are significant.

I'm wondering if I should either try to ground this wire or run another wire directly to the signal return on the pcm and splice it in just to see if it will start with the MAF plugged in...

 

[HAPPY+RANGER+GUY]

ground

Shouldn't your PCM chassis ground and battery ground be at the same level? I would expect the PCM chassis ground to read good continuity to truck chassis ground?

If that were the case your two readings would/should be the same.

 

[shr3dd3r 09]

They are. I checked them again and got the same reading. Probably was not connected good enough before. So, all connections are good to the MAF. In other news my truck won't start at all now...MAF plugged in or not... This is insane. If I take it to a dealer they will keep it for a week, find a bad connection somewhere that's a $10.00 fix, and then charge me a grand for labor for the week... That's not going to happen. This thing is grounded until I either fix it or put it into storage to be completely broken down again for a new 5.0...which is what I want to do in the long run anyway.

 

[RonD]

Might be the time to invest in a scanner, see what you get live while cranking.
For the no start I would try ether(starting fluid) and see if spark or fuel(MAF) is the issue.

Generally the PCM has it's own grounds and uses those to reference incoming signals from sensors, and as controls for things like injectors and coils.

 

[huh?]

Yes there are 6 wires. There is high resistance between this wire and the battery ground, but I can find nowhere in the wiring diagrams where this signal return wire is grounded...Unless the PCM grounds this wire through another pin. There is also a resistance reading between this wire and the PCM chassis ground, though it is extremely high. Again I can find no evidence to suggest that this wire is grounded anywhere, yet it is indeed connect to two separate grounds, though the resistances are significant.

I'm wondering if I should either try to ground this wire or run another wire directly to the signal return on the pcm and splice it in just to see if it will start with the MAF plugged in...

in my research through these vast halls of knowledge i came across a post related to this situation.

the individual(can't remember the username) posted that grounding straight to chassis(or battery) instead of through pcm would cause problems. iirc, the engine still runs but the pcm gets misinformation that will not allow it to control the engine functions properly. i'll see if i can relocate that thread.

http://oldfuelinjection.com/?p=6

http://oldfuelinjection.com/truckpinouts.html

although the diagram and list of pinouts linked to above aren't for rangers i've found they were exactly what i needed.

 

[HAPPY+RANGER+GUY]

Might be the time to invest in a scanner...

That or go heavy on the ether and then the scanner won't be needed and problem will vanish (with a whoooosh!)

 

[shr3dd3r 09]

in my research through these vast halls of knowledge i came across a post related to this situation.

the individual(can't remember the username) posted that grounding straight to chassis(or battery) instead of through pcm would cause problems. iirc, the engine still runs but the pcm gets misinformation that will not allow it to control the engine functions properly. i'll see if i can relocate that thread.

http://oldfuelinjection.com/?p=6

http://oldfuelinjection.com/truckpinouts.html

although the diagram and list of pinouts linked to above aren't for rangers i've found they were exactly what i needed.

Well in that case the wiring is correct. It's not tied directly to ground since there is quite a bit of resistance between the signal return and ground. From what I have read the signal return is a filtered ground that feeds the signals through a resistor before grounding them.

No start means spark or fuel...I'm beginning to wonder if my PATS system is causing the problem.

 

[shr3dd3r 09]

Well it starts again but only with the MAF unplugged. I don't understand. All the wires between the MAF and PCM have good connection.....

 

[shr3dd3r 09]

I discovered that the GND pin on the MAF connector and the Signal Return pin are shorted together. They are both tied to ground at the negative battery terminal. There is 0.01 Ohm's resistance between the two pins. Is this supposed to be the case?

 

[doorgunner]

I don't have any knowledge about the pins.......

but when I went thru a similar problem with my 2.9 V6 & replacing sensors, so I solved it permanently with a V-8 engine/carbuerator/distributor set-up.....

you already have the V-8

 

[feellnfroggy]

Did this ever get sorted out? I know I had a few problems all would go away by unpluggin the MAF, this doesnt mean its a MAF problem. It only means its an Emissions problem. unplugging the MAF can be a temporary fix for everything from the MAF to the EGR to the O2 sensors. IAC, etc. (i didnt read all the posts, just the first page)

 

[shr3dd3r 09]

Did this ever get sorted out? I know I had a few problems all would go away by unpluggin the MAF, this doesnt mean its a MAF problem. It only means its an Emissions problem. unplugging the MAF can be a temporary fix for everything from the MAF to the EGR to the O2 sensors. IAC, etc. (i didnt read all the posts, just the first page)

Nope. Not fixed at all. O2 sensors are new, EGR has been removed and tuned out, IAC is new, canister purge valve and solenoid are new.

 

[shr3dd3r 09]

I also wouldn't say unplugging the MAF fixes the problem. It will start and run extremely rough and still want to die. I would not even attempt to drive it like that.

My only guess is something is causing the spark timing to be way off, and unplugging the MAF only helps it because it causes the computer to use default settings....but it still runs like crap when it does start.

But that's just a theory...

 

[huh?]

I discovered that the GND pin on the MAF connector and the Signal Return pin are shorted together. They are both tied to ground at the negative battery terminal. There is 0.01 Ohm's resistance between the two pins. Is this supposed to be the case?

i would think no.

http://oldfuelinjection.com/files/EFI_harness3.gif

if you take a look at the top right there in the harness diagram it shows the return going to pin9 and a separate ground for another wire.

 

[feellnfroggy]

Does your particular motor have cam and crank sensors?