89 MJ - Only starts with no MAP Vacuum

[Divus]

I've got an 89 Comanche that I've been fighting for a few months that I've run out of ideas for.  When it was running, every few months it would decide it needed to be cranked 10-12 times before it would stay running.  A couple months ago it decided that it would no longer run at all.  I've changed out several parts and followed Cruiser's tips on ground refreshing without any luck.  The only way i can get it to run at all is with the vacuum line to the MAP unplugged.  The truck will idle in that state, but giving it anything more than the slightest gas will cause it to stall out.  I'm running out of ammunition for my parts cannon and I'm hoping someone here can get me headed in the right direction.

 

List of replaced parts:

 

IAC

Fuel Pump

Fuel Regulator

Fuel Pump Ballast Resistor

CPS

ECU

Map Sensor

EGR Solenoid

EGR valve

[Pete M]

don't forget the camshaft position sensor     it seems to be a common item that causes long cranking times.  

 

[Marine1Texas]

if it won't start with map hooked up I am assuming something wrong with the map. even if it is new could be bad or wiring. The map measures the air density going in to the throttle body. If it is not hooked up it goes to default settings for idle, however the ecu has no data on to calculate how much fuel because air density is not in the calculation. So when you hit the gas you are getting super lean and it will stall to much air not enough fuel.

 

Long cranks normal mean CPS. however a few other things. Your Ignition control modular could have bad contacts and need cleaning ( always a good think to look at. Water can get on contacts from coil to Ignition control modular and cause bad contact. Look at your coil as well. I had a coil one time work and just cut out, then work, then just cut out. Some have had just low volts get put out of the coil.

 

Of course you can't forget standard tune up parts, spark plugs, wires, cap and rotor. Also Cruiser has a indexing tip for the distributer. Also finally in your Distributor you have a Electronic Pickup called (Stator Sensor ). I have herd of them being faulty, but never ran in to that.

 

Seems like you been changing every single part and not found the reason for it running right. What I explained above is everything left. I am think to look at your wiring. Make sure rodents have not chewed on your wiring giving you problems. 

 

Like Ωhm noted below me, yes what about that TPS.

[Ωhm]

I don't see no TPS cannonball.

[Divus]

1 hour ago, Ωhm said:

I don't see no TPS cannonball.

 

I tested the TPS last weekend and it tested out fine. 

[Divus]

Checked out the coil today, contacts didn't look that bad but cleaned them up anyway.  I'm thinking I'm going to have to go hunting down wires.

[cruiser54]

Did you do Tip 5?

 

That checks the ground circuit for multiple sensors. 

[omega_rugal]

did you test the MAP? if it`s brand new maybe was DOA

[carnuck]

Did you replace fuel filter? With MAP unhooked then fuel pressure has to be up for starting.


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