Turns over but won't start

[roswell998]

93atx 112K miles

Suggestions please! The following details everything I've recently done which has a couple of thousand successful miles experience.

1. Turns over fine but won't fire.

2. No KOEO codes...nothing but 1's on both self test and stored codes.

3. Previously every week or so it might take a couple of trys to start but then it ran fine. As a result of this intermittent starting problem I checked fuel pressure a few weeks ago and it was about 41psi. I haven't checked pressure today but will tomorrow. The pump was replaced a few months ago, has worked fine and I can hear it whining for a few seconds when the key is first turned on so I expect fuel pressure to be ok but will post test results tomorrow. Also, the fuel pump relay was replaced and I know it is working fine.

4. As signature shows, both upper and front 60k's and most preventative maintenance has been done in the past few thousand miles such as; new 155 lph Walbro fuel pump, valve adjust and new cam cover/sparkplug well gaskets (no oil in wells), new AGSP32FM sparkplugs and Delco wires, new Camshaft position sensor, new timing belt, nostrils cleaned, new DPFE sensor, new throttle position sensor set to just under 1 volt.

5. Original ignition module and CPS, however, the tach has not been erratic.

Thanks

 

[projectSHO89]

Cranks but no start

Drop back to your basics: Air, Fuel, Spark, (and everything at the right time)

Air - Crack the throttle 1/4 way to see if it now fires. If so, address the Idle Air Control valve

Fuel - Does the Fuel pump prime? Can you get 36-42 psi pressure at the test port on the rail within several primes? Did the pump work at all? If you got pressure, are the injectors firing while cranking?

Spark - Connect your inductive pickup timing light to the # 1 or # 5 plug wire (they fire at the same time) and see if you get any spark. If so, is it timed correctly? (10 BTDC).

One (or more) of these tests will fail.

If SPARK:

Check for a blown IGN COIL fuse on the ATX. If blown, disconnect the low coolant level sensor before replacing..

Several have reported problems with the harness at the iginition coil opening the supply line. You can measure for coil supply at the DIS's COIL A, B, & C terminals. These terminals all should have Vbatt when the ignition key is in RUN or START and the IGN COIL fuse is good.

CPS function can be tested at the DIS module with a test indicator. rangerj posted a very good rundown a while back on how-to.

Steve

 

[bertha66]

I had a intermitant starting problems with my 93 with no codes, It was hard to start sometimes but not others. Then the fuel pump relay went out. After I fixed the relay, no more problems with it starting.

 

[roswell998]

Drop back to your basics: Air, Fuel, Spark, (and everything at the right time)

Air - Crack the throttle 1/4 way to see if it now fires. If so, address the Idle Air Control valve

Fuel - Does the Fuel pump prime? Can you get 36-42 psi pressure at the test port on the rail within several primes? Did the pump work at all? If you got pressure, are the injectors firing while cranking?

Spark - Connect your inductive pickup timing light to the # 1 or # 5 plug wire (they fire at the same time) and see if you get any spark. If so, is it timed correctly? (10 BTDC).

One (or more) of these tests will fail.

If SPARK:

Check for a blown IGN COIL fuse on the ATX. If blown, disconnect the low coolant level sensor before replacing..

Several have reported problems with the harness at the iginition coil opening the supply line. You can measure for coil supply at the DIS's COIL A, B, & C terminals. These terminals all should have Vbatt when the ignition key is in RUN or START and the IGN COIL fuse is good.

CPS function can be tested at the DIS module with a test indicator. rangerj posted a very good rundown a while back on how-to.

Steve

Fuel pressure OK at 37psi, will not start with throttle slightly depressed, ignition fuse is OK.

However,

No spark when tested with timing light. No pulse on blue lead of CPS when tested with a LED continuity testor per Rangerj's test procedure.

DOES THIS CONCLUSIVELY INDICATE BAD CPS or should I perform other diagonistic tests before replacing the CPS?

Thanks

 

[projectSHO89]

DOES THIS CONCLUSIVELY INDICATE BAD CPS or should I perform other diagonistic tests before replacing the CPS?

Almost.

Verify IGN GND integrity. O/R lead of CPS to ground.

Verify SWitched Vbatt to CPS (R/LG) sensor.

PIP, if present, should be on both the GY and DB leads of the CPS sensor.

If you have your power and ground to the sensor but no output, then the sensor is not switching as the crankshaft is rotated.

Verify mechanical condition of the sensor and vane, ie., the vane has not been damaged or has not moved outward from the block.

Check for short circuits to ground or power on both PIP signal lines before concluding the sensor is bad.

Have fun.

Steve

 

[roswell998]

Looks like CPS is indeed the culprit....what brand if Motorcraft not available?

There is both a good ground and also power with switch on going to the CPS but no switched output. I'll check for mechanical problems when tearing down tomorrow, however even if I find something like a bent vane I plan to install a new one anyway since this one is the original with 112K miles and 13 years.

QUESTION.....

If a genuine Motorcraft CPS is not available, are any after market ones considered just as good and if so which brands? Autozone about 2 miles from here has a Wells in stock.

Thanks again

 

[projectSHO89]

The Wells has been used with pretty good reliability. I'd not mess with the more expensive MC.

Make certain you set the CPS gap properly. Don't want the vane to wipe out a brand new sensor.

The harmonic balancer puller from AZ will be needed if you don't have one. It's a perfect fit (almost).

Have fun...

 

[roswell998]

The Wells has been used with pretty good reliability. I'd not mess with the more expensive MC.

Make certain you set the CPS gap properly. Don't want the vane to wipe out a brand new sensor.

The harmonic balancer puller from AZ will be needed if you don't have one. It's a perfect fit (almost).

Have fun...

Everything went fine except the fun part! We have an extremely steep driveway and this thing failed on the turn around which is on a slight incline rather than in the nice flat gargage (Could have been worse with failure on a freeway needing a tow). Felt like the side of a cliff before the job was finished.

BUT, car runs fine and thanks for the help and suggestions!