Another Crank No Start.

modulistic

Active Member
Nov 26, 2002
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Did a modfox swap and got it started before I got the interior in. Got the interior in and now I'm having crank no start. Can smell gas out the tailpipes after cranking. Have voltage at injector and cops with key on. Should the tach be moving during cranking? Pats proves out. Fuel pump primes and gives pressure. Anything I might have missed? If I'm getting gas smell out the tailpipes, is my crank pos sensor working? Fuses all good. Any ideas?
 
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No dtc codes. When key is off it won't pull codes, is this normal? Checked main engine ground on drivers side, checked ground at pcm, checked ground on dashboard frame. Pulled maf connector. Nothing.

cluster/odometer can enter test mode, also displays no dtcs.

Frustrating.
 
new battery, coil packs and plugs. no change, but wasnt expecting it to magically start up. looking like the PCM may have gotten hurt somehow.

what is the procedure for replacing/testing a different PCM? there are PATS issues to deal with, correct?
 
Crank sensor replaced. Checked pcm for burns or melts, looks ok but a chip could be fried I guess. I'm doubting every signal return could gone to :poo:. Looking like pcm though. Really don't want to :leghump: with pats.
 
I was like :leghump: it and wanted to see if I even had weak spark, so I plugged in an old coil and plug and rigged up a long ass spark plug cable to pull the plug into the car amd look for spark. Grounded it on the door frame and I was more shocked by the fact that I got shocked than the fact that I got shocked. So I bumped it again more carefully and had bright ass spark. Which realllly confused me. I was sure it wasno spark because the pump primes, I get gas spurting when I crack the fuel line, and I smell raw gas out the tailpipes wheni turn it over.

So I said :leghump:itagain. Soaked a rag in gas and stuffed it into the air inlet after the maf. Left the maf off and the son of a bitch fired off and ran great. Plugged it back together and nothing. So I'm on the right trail now. Filter or pump or Fpr or clog.

:leghump:ing mind bending.
 
Sure sounds like a possible MAF problem to me. Perhaps the MAF is over stating the air which is causing the PCM to add too much fuel.

But I have also helped a person with a similar problem. It turned out that the fuel pressure was too high. This caused too much fuel to be introduced which made the mixture too rich to fire.

What model year is this car's PCM and engine management?

What happens if the throttle is held all the way open during cranking? Part way open?
 
02 GT SOHC automatic. EVERYTHING came over from the 02. every. thing.

have tried part and fully open with no change. have tried with MAF electrically disconnected with no effect.

last night I started it with a rag soaked in gas after the MAF (leaving the MAF electrically conneted but out of the airstream), then connected up the MAF and ran it for 30 minutes to get it up to operating temp. ran great but had a really rich exhaust smell, which I attributed to gutting the rearmost cats (does this have light-off cats? I didnt even look), but perhaps its high FP? no dtcs after I cleared the p0102 (MAF code from starting it without the maf in-line) I was really hoping for it to throw a DTC to put me on the right trail. gonna bleed the brakes tonight and might spin it around the block, but im in Alaska, so I cant really do much (icy)

hmm. maybe I can try starting it with just the maf out of the airflow and no rag...

I have an aftermarket fuel rail because I damaged the stock piece and it doesnt have a schrader valve so I cant test FP, but I obviously have enough to run the motor.

perhaps fuel pump on the way out? I did run it very very low on fuel.
 
If the MAF is out of the stream, then it will report LOW. Sooooo perhaps the gas rag worked because the reported MAF value was so low that the PCM did not add any fuel injector pulse. Then the motor started and ran just on the gas rag fumes.

Normally electrically disconnecting the MAF is a quick test to trouble shoot a possible bad MAF. The trick works because when the MAF is disconnected the PCM uses default values to replace the missing MAF values. If the motor still runs rich with the MAF electrically disconnected, this suggests:
  • The PCM tune is NOT correct for the fuel injectors used.
  • The fuel pressure is too high.
  • The fuel pressure rail sensor is not sending correct valves.
  • the fuel pressure sensor intake vacuum reference line is not connected or leaks.
Once stated, the motor may be able to run because the PCM will adjust the AF ratio using the O2 sensors in closed loop mode. This will show up a large negative LTFT values.

My 2003 GT did not have a built in test port on the fuel rails. It was necessary to install an in-line piece between the fuel line and the fuel rail.

Do you have an ODB2 scanner? It would really help to know what the PCM "thinks" the Fuel pressure and MAF flow is.

I don't see HOW a bad fuel pump could cause this. Bad fuel pump is normally associated with LOW fuel pressure. The stated symptom is pig rich.

Stop guessing and test the fuel pressure. Then you will know where to focus.

OBTW, one of the more common symptoms of a bad PCM is pig rich. However I recommend replacing a PCM only as a last resort. Replacing the PCM often causes as many problems as it solves.

I also remember helping someone with a high fuel pressure problem. The cause turned out to be a ground fault in the fuel pump negative return line. This caused the fuel pump to run at 100% all of the time.
 
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ok I will work on being able to read fuel pressure.

in the meantime, want to clarify that after starting, I remove the rag and hook everything up and it will run on its own indefinetly.
the ground fault issue... would that cause the fuel pump to run full blast from key-on because it primes for a second or two then shuts off (before I crank)

I do not believe this car was ever tuned (shellac protectant still present on connector terminals underneath the plug on the PCM)

also, if I am running as rich as my nose says I am, should I be throwing 02 sensor codes for rich? It smells like my chevelle exhaust, but no raw gas dripping out the tailpipes. The reason for gutting the cats is that one side was already broken into pieces/ half blown out. dont recall this much odor though.

I will test out the signal wires for the sensor on the fuel rail and possibly replace that sensor. do you know of a diagram of which pins they go to on the PCM/ power/ ground? vaccum lines are connected and intact.

bad pcm is scaring me. dont scare me.
 
Well starts and runs now. Goofed around with the frps. So either something was goofy there or I ran out stale gas or the fuel pump unassed itself. Will see if the problem returns
 
Note, during starting the PCM runs in "open loop" mode. After starting the PCM will switch to "closed loop" mode. During closed loop mode, the O2 sensors are used. Where as during open loop mode they are not.

Also consider that a DTC will only be thrown IF the PCM realizes there's something wrong. Sooooooo if a sensor is giving incorrect signal or if the PCM is stuck in open loop, this could create a situation where the motor is running rich but the PCM doesn't know it.

Stale gas could cause hard starts as stale gas does not vaporize as well. Where as once the motor is running, the heat of normal compression improves burning of stale gas.

The best way to test the fuel pressure sensor is to ask the PCM what it "thinks" the fuel pressure is. Use an ODB2 scanner.

If interested in getting a Ford factory service manual with full wiring diagram for the 1996 through 2002 model years I maybe able to help. PM if interested.