CPS Issues

[rubiconron]

Looking for some direction here.  1988 4.0 2wd Auto Comanche.  The truck sat up for about 10 years.  Trying to get it running again.  I replaced the fuel tank and sending unit due to ethanol fuel.  I've moved on to spark and have read through cruiser's tips.  I have 3 CPSs.  One that I had in the truck before (an old Autozone unit made by Siemens) and 2 new ones.  One is a NTK and one is a Napa.  I have drilled out the old autozone one with a 3/8 drill bit and I can get .2 volts AC (it was .1v prior to drilling).  I either get 0v or .1v on both of the new ones.  I have removed the transmission and cleaned the flywheel but there is no change.  

I'm just at a loss.  Cruisers tips seem to discuss people dealing with .2-.35 readings while I have much less.  I don't really want to drill out the new sensors because I assume they will only net me a .2.  

 

I've been working on this thing in my free time for 2 weeks and I'm stuck here until I can get a cps that works.  Are these new ones defective?  Do I need to buy more?

 

Any help is appreciated.

 

Thanks,

Ron

1988 4.0 2wd Auto Comanche

[eaglescout526]

Try testing the Siemens one. That is an OEM manufacturer for those CPSs. 

[Ωhm]

You’ll need at least 300+ engine rpms during CRANK before the ECU will even think about SPARK and FUEL. Make sure battery and/or starter motor are up to the task.

[rubiconron]

42 minutes ago, eaglescout526 said:

Try testing the Siemens one. That is an OEM manufacturer for those CPSs. 

Thanks for the suggestion.  The Siemens is the one that I drilled out to allow it to sit closer to the flywheel.  Best I can get out of it is .2V.

[rubiconron]

10 minutes ago, Ωhm said:

You’ll need at least 300+ engine rpms during CRANK before the ECU will even think about SPARK and FUEL. Make sure battery and/or starter motor are up to the task.

Thank you very much for the suggestion.  I hadn't considered these items causing issues probably because they seem to be doing the job.  The battery is brand new Interstate battery 3/2022.  The starter looks rough but the engine seems to turn over very well.  It does not seem weak or slow.  I feel pretty good about the performance of both of these items. 

Thanks,

Ron

[eaglescout526]

Also grounds are an issue with these Jeeps. Make sure they are good and clean as well and the tip of the CPS can cause issues if it also isn’t clean. 

[rubiconron]

8 hours ago, eaglescout526 said:

Also grounds are an issue with these Jeeps. Make sure they are good and clean as well and the tip of the CPS can cause issues if it also isn’t clean. 

 

[rubiconron]

Just now, rubiconron said:

I have cleaned replaced and added grounds as suggested by cruiser in his tips.

 

Just now, rubiconron said:

 

 

 

 

 

[jeepmjga]

Have you tested for spark?  I only ask because I was recently having a starting issue which I thought was CPS but turned out to be a bad fuel pump.  If you have spark I would look toward fuel issues.

[cruiser54]

It's okay to drill out the other hole also. 

As mentioned above, you have verified spark?

C101 been cleaned?

[rubiconron]

On 4/6/2022 at 7:47 PM, jeepmjga said:

Have you tested for spark?  I only ask because I was recently having a starting issue which I thought was CPS but turned out to be a bad fuel pump.  If you have spark I would look toward fuel issues.

 

13 hours ago, cruiser54 said:

It's okay to drill out the other hole also. 

As mentioned above, you have verified spark?

C101 been cleaned?

I'll answer both of these together.  I have not tested for spark.  Primarily because my simplistic mind says that unless the cps (which is not plugged in) is giving out a .5V reading then everything else is secondary because it will not run without .5V generated by the cps/flywheel.  Until this problem is resolved solving other issues will make no difference in starting the truck.  If I am misunderstanding that please let me know.

Now....that being said....before I got stumped by these cps, I had started cleaning and adding grounds.  I have replaced both battery cables as well.  I did also clean out the c101 connector.  I got all of that gunk out of it.  

 

For clarity, I drilled out both sides of one of my sensors (the at least 12 year siemens sensor that came from autozone)  I have 2 new sensors that I have not drilled (one NTK that I bought on Amazon and one Napa).

 

Besides that I know I have some other issues with wiring because I have to jump the fuel pump relay to get it to fire.  But when jumped the fuel pump pumps and primes the rail.  I was going to start digging further into the wiring after I got this cps issue resolved.

 

I do appreciate everyone's time and help.  

[rubiconron]

In general if there is a logical method that I should start with to attack this thing, then I am open to suggestions.

I can get fuel.  I assumed spark was supplied by the crank position sensor but if that's not the case and I need to dive into spark then I'm game for adjusting my previous thinking.  

 

Cruiser, I know your site has a lot of tips.  Do you have some other specifics that you think will help?  Obviously I need spark.

[cruiser54]

Spark is actually supplied by the coil. The ECU fires the coil after knowing the CPS is sending the correct signal.

As stated in my write-up on CPSs, you don't necessarily have to get the full .5. .35 may work. 

[Ωhm]

Using a voltmeter or 12vdc testlight (preferred) check for Battery_Voltage_(B+) on the following pins (use battery_negative terminal for ground):
D1_5:  B+ (Hot at all times)
D2_4:  B+ (Hot during KEY ON/CRANKING).
D1_6:  KEY ON (B+ (Hot for 2-3 seconds)) or CRANKING (B+ (Hot during CRANK)).
 

 

[jeepmjga]

When I tested my CPS I was even getting .27v but still getting spark.  Have you replaced the fuel pump relay? An inline spark tester from a big box store should be pretty cheap just to help verify that part of it.  The diagnostic connectors should tell you a lot as Ohm suggested.  When you jump the relay and get the fuel pump to run is the motor firing up?  Just to clarify what exactly is happening when you are trying to start it?  Can you hear the fuel pump turn on and prime when you turn the key on?  Is it a crank no start condition or a no crank condition?