Electrical/injector Help.... I'm Stumped

[Jpyke]

Hey everybody I'm new to the forums but not to the mustang world. Any help would be much appreciated.

Ok so I have a 96 gt donor engine with the stock harness computer etc. The engine computer/ harness has been transplanted into a ford ranger along with the mustang dash instrument cluster steering column etc. everything was running perfect and smooth until one day I had the dash loose while it was running and it sorta dropped on the driver side. It stayed running until I cut it off . Fired right back up then died. Turned the key off back on runs for a second or two then dies. This happens every time no matter what. Hooked up a noid light and the injectors are loosing pulse after a couple seconds causing the engine to die. I pulled the dash and didn't see any prob with wires? Any suggestions I'm thinking ccrm or prob computer

 

[wmburns]

Turn the key on but do NOT crank. Does the theft light go off after a 3 second "prove out"?

Do you have an ODB2 scanner? If so, it would help to monitor RPM's while cranking. We are expecting the RPM's to change when the motor is cranked. I'm also interested to know what the RPM's are doing when the motor dies.

While monitoring also look at the PCM operating mode (open or closed loop). It may give an important clue if the motor dies when going from open loop to closed loop.

 

[Jpyke]

No the theft light flashes. I've already had a chip burned to disable pats. Didn't change anything. Every now and then it will crank and run fine but rarely. Hooked a scanner up and it shows no codes. I don't know about a odb2 scanner is that the same as a code scanner?

 

[Jpyke]

And I thought if pats was acting up it wouldn't start at all?

 

[squeak93]

If Pats is disabled and NO codes, then you need to look for a broken/bare wire or loose ground.

Can you elaborate what you mean by the dash sorta dropped?

 

[Jpyke]

If Pats is disabled and NO codes, then you need to look for a broken/bare wire or loose ground.

Can you elaborate what you mean by the dash sorta dropped?

The dash was just sitting in place with nothing holding it in place and it fell off the firewall. When it fires up it runs smooth with no jump in rpm then just dies like the key is cut off

 

[wmburns]

Do you have a set of 96 wiring diagrams?

Do you have a Volt-Ohm Meter (VOM) and are you willing to use it? If so, get your self an "add a fuse" as there are some key circuits that need to be monitored to see if power is dropping.

It would also help to measure the key off resistance of every black wire and black wire with a white stripe back to battery negative. The Ohm value should be low.

FWI, an ODB2 reader and scanner are different. The reader can only access DTC codes. The scanner can access DTC codes as well as operational PID's. Advanced units can even data log.

 

[Jpyke]

No wiring diagram and yes on the volt ohm meter. Are you talking about every black black/white wire or just the ones coming from ecu? Also what it this "add a fuse"?

 

[Jpyke]

Checked all the black. Black/white wires from the ecu and the highest reading I got was a 15. I assume that's low. Any other suggestions. Should I test anything at the ccrm?

 

[wmburns]

15 Ohm's for a ground is high. It should be way less than 5 Ohms. I'm assuming that you calibrated/zeroed the Meter first and used a new battery in the VOM.

Also need the measurements on the black wires from the cluster.

Here's some examples of "add a fuse". It's an easy way to tap into a specific circuit and attach a VOM for monitoring.

http://www.amazon.com/dp/B009K6ZH6W/?tag=stangnet-20

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=BK_7822226_0361086491

search Google for "add a fuse images".

Further trouble shooting is going to get difficult without a set of wiring diagrams. If interested in getting a set for yourself I maybe able to help. PM if interested,

 

[Jpyke]

Could a faulty ccrm be causing this ?

 

[wmburns]

Have you ever heard of Occam's razor?

http://en.wikipedia.org/wiki/Occam's_razor

What you are suggesting is that the CCRM picked the exact moment that you dropped the dash to go bad. One heck of a coincidence wouldn't you say????? Wouldn't it be more likely to have something to do with the Cluster or Ignition switch? Or maybe a blown fuse?

It sounds like you are trying to drop into "parts changing" mode. IMO the CCRM is an expensive part to swap out just for diagnostic reasons. There are tests that can be done with a simple VOM meter, a few scrap pieces of wire, and add a fuse and a set of wiring diagrams that will can rule in/out a bad CCRM.

It's seems to me that anyone capable of transplanting a Mustang wiring harness into a Ranger should be able to trouble shoot this electrical problem. But it's your project and $$.

What happens if you disconnect the MAF electrical connector?

Do you have an ODB2 scanner?

 

[Jpyke]

Coincidence...yes. Possible......yes. I know better than to just start dropping in new parts. What makes me think it "might" be the ccrm is I know the fuel pump relay went out(it's now on a switch) and so did the fan. If i unplug the maf sensor it's the same thing along with tps and iac. And no I don't have a odb2 scanner. I'm getting 35psi fuel pressure and constant spark no matter what. I'm 95% sure it's a short in the wiring somewhere. That's what scares me because I'm no electrician/technician. Again thank you for all the help. I'm going to purchase a "add a fuse" and try to figure this out. Again thank you for your time

 

[wmburns]

It "might" have been handy to "mention" the "other" symptoms......... <picks up chair>

But remember that the CCRM needs a signal to tell it what to do. The CCRM could be working just fine but the signal is missing.

If having trouble with multiple subsystems that all pass through the CCRM (fuel pump, cooling fan, ignition, PCM power), I would 1st be thinking bad/weak CCRM ground. Especially when one of the previous posts mentioned a very high ground resistance of 15 Ohms..........

Consider monitoring for +12 volts at the engine mounted radio interference capacitor. There should be a solid 12 volts the entire time the key is on. Does the voltage drop when the motor dies?

 

[Jpyke]

I've checked all grounds/connections and all seem to be fine. Like you said its a slim chance the PCM relay failed the same time I had the dash issue. And also if the ccrm/PCM relay failed would it not shut the PCM down completely. I'm still getting constant spark and I'm getting injector pulse for a second or two which tells me (not a technician) that the PCM is working

 

[wmburns]

One thing that you may not be taking into account is the CCRM is actually several internal relays packaged on a PC board. Therefore it's POSSIBLE to have a partial failure of the CCRM.

IF the only thing going away is the injector pulse, then there's a very limited set of possibilities.

• Anti-theft (PATS)
• Unstable CKP sensor signal. Which if true would also mean that the ignition would quit as well.
• Bad PCM

The power for the injectors goes through the PCM. So for the 96 MY, there isn't a CCRM failure mode that can only take out ONLY the injectors. A CCRM problem would take out the PCM as well.

Guess where part of the PATS system is?............What for it. The cluster.

Since this problem started when the cluster was dropped/bumped, a PATS/Anti-theft related issue can't be ruled out.

 

[Jpyke]

I thought the same thing. Had a chip burned to disable pats and nothing changed

 

[Jpyke]

Also if it was a pats problem would I still be getting spark and a initial injector pulse

 

[wmburns]

FWIIW, PATS works by with holding the injector pulse. So the the assumption that this couldn't be PATS isn't entirely true. However, it's hard to ignore PATS being disabled in the PCM. The fact that it starts at all also tends to point away from a PATS issue.

Note that I said "IF" the only thing wrong was........However in this case it's not completely true. There's other "strange" symptoms that haven't been fully disclosed thus creating less than educated guesses.

For example, earlier posts report a sky high ground resistance of 15 Ohm's. Later posts say that the grounds are "good" with no mention of how the measurement was done. It certainly appears that the cause for the high ground measurement was never chased down or understood. We are dealing with a Frankenstein install. Have you accounted for ALL of the grounds through out the car? The high ground resistance back to battery negative says NO!

A visual check of the grounds is not going to confirm a ground that you do not know about. The only real method is be actually measuring the Ohms back to battery negative. The value should be less than 5 Ohms.

Bottom line. Today's cars simply will not run right without a strong battery and charging system. The vast number of electrical systems in the car demand a stable supply voltage. Excessive ground resistance will cause the voltage at the point of use to drop as the load increases. Cut corners here at your own risk!

One of the other control circuits that does pass through the cluster is the Alternator charging monitor. What is the voltage at the battery? When the motor starts, is the alternator putting out?

If you had access to an ODB2 scanner some vital information would be easy to get. For example if we confirmed a stable RPM signal. Perhaps the motor is quitting when the PCM switches from open loop to closed loop. Monitoring the PCM mode could quickly rule this in/out. What is the MAF value? If too low, this could cause the motor to quit during closed loop processing.

 

[Jpyke]

We'll this is a Frankenstein install but it was running for months before this happened. When I said all grounds were good I was referring to where they connect to the body/battery(nothing loose etc). The alternator is brand new. But that doesn't mean it's working properly. Even so if the battery was at full charge it would run without the alternator even hooked up(I've done it before on this setup). I'll see what I can do about getting a obd2 scanner and another meter as the one I have borrowed May not be calibrated