Intermittent no start

[jeepmjga]

Hey all, so before I shell out dough on ANOTHER CPS, wondering if anyone has any suggestions.  Got an intermittent no start/rough start condition.  If the truck sits for a while I will have a very long crank time but usually it will start and run fine.  If I go out to run errands or such I am getting a very rough start/no start condition for a few tries, but eventually it starts and runs normal.  I replaced cps during the build and tested that one with a reading of .32 volts, so replaced again with a NAPA sensor, again same reading of .32 volts.  Drilled out the top hole on both sensors and got up to .44v on both sensors after that, no change in start status.  Just went out and did total ground refresh again, also made sure mating surface to bellhousing was clean.  Condition started randomly about a month ago while out and about.  Anyone got any suggestions before I fork out some $$ for a mopar sensor?  All fuel system components are less than 1000 miles old except injectors (mustang injectors), new MAP, TPS, IAC, plugs/wires, cap/rotor, NGK coil, brand new Optima red top, but as I said it runs great once its started.  Thanks everyone!

[JustEmptyEveryPocket]

Have you checked for spark during your long initial crank times? That would verify CPS. Then what about fuel pressure? Both of those checks done during crank after sitting and when the problem occurs. At least that is where I would start.

[cruiser54]

I'd be looking at fuel issues. 

 

How old are the plugs, wires, cap and rotor? 

[jeepmjga]

16 hours ago, JustEmptyEveryPocket said:

Have you checked for spark during your long initial crank times? That would verify CPS. Then what about fuel pressure? Both of those checks done during crank after sitting and when the problem occurs. At least that is where I would start.

 

Ill check both of those next, I thought about fuel related but it runs great when its running, I can hear the fuel pump turning on and priming when I turn the key and all the fuel components are new.  I'll ave to recheck all the connectors under there too.

4 hours ago, cruiser54 said:

I'd be looking at fuel issues. 

 

How old are the plus, wires, cap and rotor? 

 

All less than 1000 miles old.  Any other reason than bad sensor you think I'd be getting less .5v on the cps?

[MiNi Beast]

Pump may work but pressure regulator on the rail may be dirty causeing the check valve to leak causing the fuel to drain and loss of pressure. And or your mustang injectors dumping to much fuel in the start up. 

[cruiser54]

22 hours ago, jeepmjga said:

 

Ill check both of those next, I thought about fuel related but it runs great when its running, I can hear the fuel pump turning on and priming when I turn the key and all the fuel components are new.  I'll ave to recheck all the connectors under there too.

 

All less than 1000 miles old.  Any other reason than bad sensor you think I'd be getting less .5v on the cps?

Have you visited my website and completed Tips 1 through 5 yet? If not, begin there before doing anything else. 

[jeepmjga]

19 hours ago, MiNi Beast said:

Pump may work but pressure regulator on the rail may be dirty causeing the check valve to leak causing the fuel to drain and loss of pressure. And or your mustang injectors dumping to much fuel in the start up. 

 

Got a new regulator otw, ill check the pressures on Tuesday when I have some time and see what I get. 

 

6 hours ago, cruiser54 said:

Have you visited my website and completed Tips 1 through 5 yet? If not, begin there before doing anything else. 

 

Yes, also replaced the braided ground cable and added the extra ground cable to the radiator cross member bolt. Just re-refreshed all the grounds a couple days ago as well. Will check the ecu harnesses on tuesday as well. 

 

So small update, I straight wired the older sensor to the harness wires just temporarily to eliminate the possibility of a bad connector and got no change in results. Rewired the connector back in,  installed NEWER cps, (also drilled to 3/8) and now am getting no start and only 2.8v to cps.

 

Is there anywhere to still get a mopar cps and if so is there a part number out there? Having trouble finding a solid answer. Thanks for the suggestions so far everyone. 

[cruiser54]

Are you getting spark?

[jeepmjga]

On 3/19/2022 at 6:28 PM, cruiser54 said:

Are you getting spark?

 

Had time to mess around with it today. Yes I have spark but now the fuel pump is NOT turning on at all. I guess i was hearing something else when I turn on the ignition. Tested small diag connector pin with circuit tester, the light is constant on when i first turn the key for a few seconds (for prime i assume) and when cranking its stays constant. Tried jumping the relay and still not getting any power to pump. Ballast resistor is intact and terminals are clean, fusible link from the icm looks good still. Connector close to the tank looks to be in good shape, pump was replaced as the first part of the build/resto. Unfortunately i have close to a full tank in it so was wondering thoughts before i drain and pull the pump?

 

Edit: the ground behind the taillight is clean, shiny and tight. 

[cruiser54]

Check voltage at the pump harness. 

[jeepmjga]

16 minutes ago, cruiser54 said:

Check voltage at the pump harness. 

 

Best to backprobe connector while connected or check at pins in connector from engine side? I should be getting +/- 12v while cranking right? Thanks for your time, I'm still learning electrical stuff, never been my strong suit.

[cruiser54]

do both!! You're on the right track. 

[Fryedaddy]

What year is it? Check the fuel pump ballast if its an early model. I removed mine all together and placed a fuse in the wire clips. 

[jeepmjga]

1 hour ago, Fryedaddy said:

What year is it? Check the fuel pump ballast if its an early model. I removed mine all together and placed a fuse in the wire clips. 

 

Its an 89, ballast resistor is good.

[jeepmjga]

Well did some more testing today. Had power back to the connector harness from the engine side but not when backprobing the pump side connector. Had a spare battery laying around so wired it directly to the battery to test, pump turns on but does not pump anything. Pulled it and checked the wiring, found a knicked gauge sending unit ground but all other wires looked ok. Ordered a new carter pump kit so hopefully that solves it. Kind of miffed why it would just not pump anything all of a sudden? Wired in reverse it pumps in reverse but will not pump anything through it when putting power to it in the normal order. Also installed new pressure regulator just because. 

[cruiser54]

If that rubber hose has a hole/kink/split, loose clamp,  it won't pump fuel. 

[jeepmjga]

Well a new Carter pump and I'm back on the road, definitely a good learning experience.  Thanks for the help everyone, now I'll get to wheel a little this weekend!