So i bought a 51 Whilly

[Binder]

so i got a scan tool that does OBD II and will also do OBD I....i ran the scan and i think i found my problem, my map senser has three wires to it purple - ltgreen - grey.

it shows 4.99V at idle and should show very little at idle and 4.99 at WOT.

i look at all the diagrams and the wires should be
ltgreen - purple - grey....purple wire should be in the middle i believe the reference voltage and enable voltage wires are swapped at the connecter.





ill call the wiring place again tomorrow they have been very helpful on the phone.

Sounds like you're on to something.
It should show 5 volts with the engine off which would be about the same as WOT. Like you said, at idle/ high vacuum the volts should be very low.....

 

[zukkev]

The PCM uses information from the MAP sensor to calculate spark advance and fuel as follows:

* Low MAP output voltage (low pressure) results in more spark advance.
* High MAP output voltage (high pressure) results in less spark advance.
* Low MAP output voltage (low pressure) results in less fuel.
* High MAP output voltage (high pressure) results in more fuel.

OPERATION
The control module supplies a 5 volt reference signal to the MAP sensor and the sensor provides a path to ground through its variable resistor. The control module by monitoring the sensor output voltage can determine the manifold pressure. A closed throttle on engine coastdown will produce a relatively low MAP output, while a wide open throttle will produce a high output. At higher pressure or at Wide Open Throttle (WOT) output voltage will be about 4 to 4.8 volts. The higher the MAP voltage output the lower the engine vacuum, which requires more fuel. The lower the MAP voltage output the higher the engine vacuum. At lower pressure output voltage will be about 1 to 2 volts at idle.


If you can read a diagram....you should be able to figure out which goes where....Basically 5V ref is the gray wire, pin C on the plug...signal is Bl/lt grn Pin B (middle).... sensor ground purple is Pin A.....

 

[Hip]

If you can read a diagram....you should be able to figure out which goes where....Basically 5V ref is the gray wire, pin C on the plug...signal is Bl/lt grn Pin B (middle).... sensor ground purple is Pin A.....

well crap that IS how mine is wired.

 

[ain'tstuckjustresting]

your issue sounds like a leaky injector or CPI spider?

Have you popped off the upper intake and looked for clean spots or puddled gas?

Yep, it does and I changed the spider & nut kit 1st thing. No fuel in the intake before and none now

My Map is wired just like the diagram and I tested it Sunday seems OK. This is going to drive me nutty. (Nuttier)

 

[zukkev]

well crap that IS how mine is wired.

Ok, do you have a vacuum pump? If you do, take it and connect it to the MAP sensor port, turn the key on---and with a meter hooked up to the signal wire (red lead to the signal wire) and the black lead to the sensor ground, apply vacuum to the MAP, if the signal voltage doesn't change as you increase vacuum to the MAP port; switch the ground lead of the meter to another (engine) ground and redo the test---if it still doesn't change=bad MAP; if it does change on the second test, then you have a problem with the sensor ground from the PCM...

 

[Hip]

Ok, do you have a vacuum pump? If you do, take it and connect it to the MAP sensor port, turn the key on---and with a meter hooked up to the signal wire (red lead to the signal wire) and the black lead to the sensor ground, apply vacuum to the MAP, if the signal voltage doesn't change as you increase vacuum to the MAP port; switch the ground lead of the meter to another (engine) ground and redo the test---if it still doesn't change=bad MAP; if it does change on the second test, then you have a problem with the sensor ground from the PCM...

i believe i have a problem with the 5V signal cause its 11.5 V, just got off the phone with the wireing people and they want me to try another PCM, i have one driving over as we speak.:awesomework:

they want me to check signal voltage at the other sensers also but 11.45 is to much.


i did the above test and the map senser can control voltage its just all too high. it starts at 4.99V @ 20"u and goes up from there to 10.5V@ 0"u..

should start low and climb up to the 5 V ref but not higher.

ya'll grab a :beer: and some :corn: and watch me scratch my eyes out:flipoff:

 

[jeepmauler]

You know who is kicking around the area and could probably help? Trevor from S-N. He wired pretty much every buggy that left that place and most had the 4.3......you may want to track him down for a stop by.....or not.

 

[Hip]

You know who is kicking around the area and could probably help? Trevor from S-N. He wired pretty much every buggy that left that place and most had the 4.3......you may want to track him down for a stop by.....or not.

i would love to, do you have a number for him or way to contact?

i tried another new PCM and still have 11.57V for control

all the other control voltage appears to be 5 V.

 

[Binder]

i would love to, do you have a number for him or way to contact?

i tried another new PCM and still have 11.57V for control

all the other control voltage appears to be 5 V.

Sounds like the harness is screwed up. They probably have the MAP power hooked to the injector power.

 

[Binder]

The picture attached in Kevins post #676 keeps changing.:eeek:....Maybe it'll change to some good porn if we wait long enough?

 

[crash2]

Could be a baro sensor too. Some of them are keyed the same(connector) and are backwards..

 

[crash2]

The picture attached in Kevins post #676 keeps changing.:eeek:....Maybe it'll change to some good porn if we wait long enough?

Huh--your post is # 650

 

[Binder]

Huh--your post is # 650

OK 642.:flipoff:

 

[Hip]

yeah in another thread saveahoe i posted a link to a diagnostic dwg that also kept changing. each time i looked at it it was another drawing from a chevy repair site.....

the hyper link takes ya to thier page but you see what ever is up there being viewed by someone else??

 

[Hip]

ok i disconnected each end and did a continuity check and it is the right wire connected to the correct pin on the ECU plug. pin 14. verified my old harness and it is the same. the new ECU still gives me 11.5V?

disconnected all power from everything and did a continuity check to all power wires from the ref volt to the MAP.

no cross bleed at all.

should i just try jumping the 5V ref from the throttle pos senser to the map ref?

they do each have thier own wire all the way to the ECU plug so thats probably not the corrrect answer.

 

[zukkev]

The picture attached in Kevins post #676 keeps changing.:eeek:....Maybe it'll change to some good porn if we wait long enough?

Well, I'll be damned, it DID change!:haha:
I deleted the links before the porn shows up!:redneck: (
(likely a security thing for alldata....)

 

[zukkev]

Hey, another thought, is there another sensor somewhere in the vicinity of the MAP that uses the same connector (Mike brought up a good point)??? I seem to remember something about getting the two plugs mixed up can cause a similar issue you're experiencing...

 

[Hip]

Hey, another thought, is there another sensor somewhere in the vicinity of the MAP that uses the same connector (Mike brought up a good point)??? I seem to remember something about getting the two plugs mixed up can cause a similar issue you're experiencing...

naw i dont think so in this case as i traced the individual wire

it matches the OEM plug exactly.

so if the ECU produces the signal voltage and i changed the ECU and its still the same?

when at the parts store they asked me what serial number as there were two different ones could one versin be different?

im ready to rip the ecu out of my friends blazer that i tested today that has 5V and try that.

zukev do you have access to the alldata link posted above? if so can you show a pin dia of the ecu? you know what pin number is supposed to be to what?

 

[Binder]

naw i dont think so in this case as i traced the individual wire

it matches the OEM plug exactly.

so if the ECU produces the signal voltage and i changed the ECU and its still the same?

No it doesn't make sense. What is the SN of the PCM?

 

[Hip]

No it doesn't make sense. What is the SN of the PCM?

16168625 is what i have
16197427 is the other option:scratchhead:

never mind on the pin diag i got one now. ill break out the magnifying glass and go over everything tomorrow. :thud: