Completed installation of a timing gear & chain, water pump, fuel fileter, dist. cap., wiring, and new plugs -- in trying to start up had a difficult time trying to get the engine to run. I've remove the MAP Sensor wiring -- and the engine will start, and run fairly smooth: Can someone outline the test procedure for jumping out the leads on the MAP sensor to see if my problem is the MAP sensor or MAF sensor? Thanks

 

Sound like it's the MAP sensor. When you unplug it, you more or less put the computer into "Safe-Mode" and it uses approximate values for the sensor readings. This should trigger a CEL as well.

I'll try to check my factory service manual tonight and see if it mentions any testing method other than plugging the CPU into a computer.

BTW, the '89 truck 5.0 doesn't have a MAF sensor.

 

Thanks - I located the SPOUT connector: just taped up within the wiring harness: with the SPOUT connector removed - I've been able to crank the engine - able to increase the rpm's - and the engine run smooth across the various rpm bands: As soon as I reconnect the SPOUT the engine runs rough, and irregular: Working in the tight van compartment -I'm having a tough time spotting the timing mark.

Going from running smooth (no missing, and or backfire) without the SPOUT, and then to running rough with SPOUT installed (no check engine light - code scanner is giving me a all clear with the KOEO test.

Could my problem be the Electronic Control Module? -- Can you suggest the next test steps?

 

Set your timing with a timing light with the SPOUT out at 10* BTDC.

 

I had turned the distributor base as far clockwise as it would go: with the SPOUT out the engine is running ok -- however I'm not able to spot my timing mark: my initial set up was with engine off - no. 1 cylinder @ tdc - rotor pointing @ no. 1 port:

To give me some adjustment with the distributor - I advanced all plug wires on the distributor one space in the clockwise direction: with engine running I now have my timing mark hitting around 10 degrees btdc with the SPOUT out - with the SPOUT in it's the timing mark is holding: engine runs smooth thru various rpm ranges:

To be able to get the number 1 plug lead back on the no. 1 marking for the distributor - is this telling me that I need to pull the distributor and rotate the distributor one gear notch clockwise, and then back the plug wire back one counter clockwise to realign no. 1 plug wire with the number 1 port on the distributor cap?

What has me puzzled is why was no. one off so when I had made all the allignments @ tdc for no 1 piston, and distributor rotor was set to no. 1 port. by having to move no. 1 wiring plug clockwise by one - with my initial setting - I guess I was firing late, and by movng the plug wire clockwise by one -- number 1 cylinder is timed to fire @ 10d btdc.

 

Sounds like maybe your valve timing is off a little.

 

I had checked by compression on a couple of cylinders prior to all the start-up attempts -- compression is good confirming crank, and cam timing for the valves: Not being able to advance the distributor any futher, and not seeing the timing mark -- I rotated the sparkplug leads clockwise to pick up the additional advance: sure enough there was my timing makr appearing close to the block pointer:

Marked the base of the distributor to maintain same alignment - pulled the distributor shaft rotated the shaft counter clockwise one tooth, and reinstalled: then rotated the plug wires counter clockwise to have proper alignment of no. 1 plug wire with the 1 on the rotor cap.: Cranked her over -- and there we are with the SPOUT plug back in & our timing mark being maintained in the area of 11 degrees advance: runs smooth thru various rpm bands: Close to have the 5.0 back on the road: Thanks for all the comments: