Is there a Ford Tech out there? Need OEM EFI info

7423 · 10-09-2009, 08:58 PM

1995 Mustang 5.0. Using the OEM computer, injectors, air meter and throttle body. At times, with out warning, the fuel pump will stay in prime mode when the key is on, engine off. (Normally it would cycle on for 2-3 seconds and the shut off). When it malfunctions, injectors are wide open and if the car starts, it is waaaay fat and barely runs and throws a CEL. Oddly enough, there are no codes to read. Shut the key off and back on several times and all is well, the pump will cycle and run normal when started. I have swapped the ECM, no change. I believe something is telling the injectors to go rich which runs the pump.
Any ideas??
Thanks much in advance

Dave Noll · 10-10-2009, 04:25 PM

I would start by disconnecting the ignition module when this is acting up & see if the injectors shut & FP kicks off. Several times I have seen an errant RPM signal coming out of the module that could be attributed to one of 2 things, either a bad module ( that will still allow the car to run ) or a magnetized distributor shaft.

Moparteacher · 10-11-2009, 11:41 AM

Swap or replace the fuel pump relay. The car may have a fuel pump module with an integrated relay. The relay me be sticking.

A stuck or dirty injector can cause the misfire.

The injectors normally don't open without a cam signal (cranking or running). Faulty ignition module is a good guess.

If the CEL is on then there is a code (if OBDII) Many Fords were OBDII in 95'. The code may be a factory code and requires a scan tool with enhanced reading capabilities. Generic scan tools will not read factory codes. (OBDII).

Most quality scan tools have a "movie" mode for recording parameters over time. The NGS would be the preffered tool.

All this is nice to know but in the real world the typical Ford diagnostic charts almost always ends with "replace with a known good part"........so just swap some parts first.

10-09-2009, 08:58 PM	#1
7423 Senior Member Join Date: Dec 2006 Posts: 640 Likes: 0 Liked 1 Time in 1 Post	Is there a Ford Tech out there? Need OEM EFI info 1995 Mustang 5.0. Using the OEM computer, injectors, air meter and throttle body. At times, with out warning, the fuel pump will stay in prime mode when the key is on, engine off. (Normally it would cycle on for 2-3 seconds and the shut off). When it malfunctions, injectors are wide open and if the car starts, it is waaaay fat and barely runs and throws a CEL. Oddly enough, there are no codes to read. Shut the key off and back on several times and all is well, the pump will cycle and run normal when started. I have swapped the ECM, no change. I believe something is telling the injectors to go rich which runs the pump. Any ideas?? Thanks much in advance

10-10-2009, 04:25 PM	#2
Dave Noll Senior Member Join Date: Nov 2007 Location: Div. 6, Eastern, WA Posts: 694 Likes: 2,260 Liked 219 Times in 105 Posts	Re: Is there a Ford Tech out there? Need OEM EFI info I would start by disconnecting the ignition module when this is acting up & see if the injectors shut & FP kicks off. Several times I have seen an errant RPM signal coming out of the module that could be attributed to one of 2 things, either a bad module ( that will still allow the car to run ) or a magnetized distributor shaft. __________________ Dave Noll, E/FS ,L/SA 6526

10-11-2009, 11:41 AM	#3
Moparteacher Junior Member Join Date: Nov 2007 Location: Boise Posts: 49 Likes: 0 Liked 0 Times in 0 Posts	Re: Is there a Ford Tech out there? Need OEM EFI info Swap or replace the fuel pump relay. The car may have a fuel pump module with an integrated relay. The relay me be sticking. A stuck or dirty injector can cause the misfire. The injectors normally don't open without a cam signal (cranking or running). Faulty ignition module is a good guess. If the CEL is on then there is a code (if OBDII) Many Fords were OBDII in 95'. The code may be a factory code and requires a scan tool with enhanced reading capabilities. Generic scan tools will not read factory codes. (OBDII). Most quality scan tools have a "movie" mode for recording parameters over time. The NGS would be the preffered tool. All this is nice to know but in the real world the typical Ford diagnostic charts almost always ends with "replace with a known good part"........so just swap some parts first. __________________ Gary Weaver Moparteacher@yahoo.com Last edited by Moparteacher; 10-11-2009 at 11:44 AM.