New member,old mechanic. I am 82 years old and retired from class A mechanic in 1971. Never worked on an ECM car until I got this 1993Ford Ranger 4x43L v6. I have done some work on it to no avail. My hope is after reading this rather long story someone will have see this problem before or will be able to diagnose this problem for me. This should be a new paragraph but I can’t operate this computer either…..I bought the truck as is and drove it 75km. Home,ran perfect A few days later I noticed it cranked longer before start, each day it took a little longer. This old man figures gas leaking back into the tank so I just waited until pump quit and starts right up each time I started it hot or cold it would take longer for pump to stop. I know it should run only a few seconds so this started the old coges in My brain to turn. Here is what I wasted my time and Money at! NEW FUEL PUMP,no difference. NEW FUEL REGULATOR,no difference. Here is what it does and her is what I have checked. On the. rare occasion for no apparent reason everything seams normal and the truck will start and run perfect, once every 3 or 4 days. I try it about 10 times a day. NOW COMES THE WEIRD STUFF. If I try to start it with the fuel pump running it won’t start. EXCEPT !!!!! Once in a few 100 tries! In that once in a100 it runs rough.Now here is what is normal . Turn the key on,pump starts. Jets are ok, tested separately they open and close with applied voltage.Fuel pressure 38 lbs. and holding ,vacum holds. After cranking plugs are dry. My amateur diagnosis is something isn’t telling the injectors to open. BUT WHAT. MORE WEARD CLUES. In this no run normal state, fuel pressure good, vacum e good, fuel pump runs (won’t shut off) if key on,engine light is on,brake light is on and worst of all,engine light stays on will not flash codes. I ordered a 1 reader not her yet, may not work either. NEED HELP. THANK’s FRUSTRATED

 

I had something like that in away. '93 ranger. I couldn't get the codes and had bad fuel milage. it turned out to be the PCM. I took it out and then took it apart. then took pictures of it apart and set to a friend. he could see there were 2 capacitors that were bad. I didnt fix it but I hear it's not too bad. I ordered a new one put it in and bingo, all good. I think you can find info here on what a bad one would look like. good luck!

 

Follow up to above. Today truck starts,runs rough,fuel pump run’s constantly engine light stays all the time and dbd1 ***** communicate with computer.

 

Correction dbd1 will NOT CONNECT TO COMPUTER

 

I believe there’s a couple ways to get the codes from OBD1. Where does your meter plug into?

 

PCM diode or fp relay

 

There are a bunch of websites and YouTube videos showing how to read OBD1 codes with a meter or using the check engine light. Here's some examples. The Haynes manuals do a good job of explaining what to expect (long pauses vs short pauses, etc.) and also both the key on engine off (KOEO) and engine running test. Although, I've never been successful at the engine running test.

https://obdadvisor.com/codes/how-to-read-obd1-codes/ - basic but a good start
https://www.troublecodes.net/ford/ - a lot of info but has the code descriptions, referenced in the video

 

When the key is on, the relay will have power to it continuously. If it has an internal short the pump will keep running, overheating the relay and the diode. If the PCM isn't happy it won't send fuel or spark.

 

Newer relays have the diode built in.

 

when you say PCM i assume you are talking about the main computer? cause i have similar symptoms, although i need to rebuild my engine so it might not be that, just wondering.

 

yes, there is a way to check

 

ok, i think i will run some diagnostics next time i have access to a garage