Engine won't start

[rtamboli]

My 1994 2.3L SFI (California only) won't start all the time.

I purchased a replacement motor and did not know enough to look at all the connectors on the harness. The old harness is no longer available.

There is no connector for the cam position sensor on this harness and the motor came with a cover over the mount hole for the cam sensor.
Is the cam position sensor required? Why would the mount have been blocked?

The truck ran but it would die randomly at any time, it would start everyday for weeks then it would not start, then the next time I tried it would start. my 1994 2.3l sfi (california) Ranger xlt pick up
I have changed the fuel pump, the fuel relays, the PCM, the MAFS.
The last thing I did was change out the PCM and then it ran for one night and now will not start again.

With the ignition on the fuel pump is not running, if I jump the inertia switch it still does not actuate the fuel pump. If I jump the relay and power the pump it won't start any way. There is spark but it seems a bit weak, but as I mentioned it seems to run just fine intermittently.

I am at the end of my skill set here any suggestions would be great.

If you need any more information please just ask I will gladly provide what information I can.

Thanks Rick

 

[Mark_88]

Welcome to TRS Rick~!

Probably not able to help you, but just to clarify, what year engine did you replace the 94 with, and did you get the wiring harness and computer from that vehicle?

Intermittent starts, in my experience, have been related to either battery or fuel delivery in most cases...but you didn't mention what the truck does when it doesn't start...does it just crank and not fire, or does it not even crank?

If it does crank, does it catch at any point and then die or does it simply not catch?

 

[adsm08]

The cam sensor is kinda sorta important. It's what the computer uses to identify the cylinder and stroke. Batch fire systems didn't have a cam sensor because it wasn't important to know what stroke a given cylinder was on, only to know when cylinder 1 was coming to the top.

If it dies on start up but runs fine once your check engine light comes on I would say it's a pretty good bet that your missing cam sensor is to blame. If it dies after it's been running for a bit you might have other issues.

I have a similar problem in my 87. I have a 92 engine (batch fire setup) with a 94 harness and computer (sequential fire setup). It sputters and dies right after start up every so often. I know it's because I have not gotten a cam sensor installed yet, because it goes back to a batch fire strategy after it realizes it won't get the cam signal.

 

[Road Angels]

Shot in the dark with available info Ign. switch, when you first turn the key to the run postion not the crank postion do you here the fuel pump prime for about 2 seconds or so, is spark blue or orange in color, orange is weak spark, also check at the schrader valve to see if you have fuel pressure after jumping at the diagnostic connector, use a rag and a small screw driver, it looks like a tire valve on the fuel rail, rags to keep gas it from getting all over you, if you got fuel, correct spark timing and compression it shoud go, and since it goes at times, start checking your connections, pull apart and reconnect

 

[rtamboli]

All of this input is great, thanks. When I turn it over that is all it does no catching no sputtering just crank as if it was going to start. I have checked fuel pressure and I went as far as to take the grounds all off and remove paint to be certain grounds are good. I have cleaned each connector and traced everything out using the Ford wiring diagrams.
I really think it is the brain again but I don't want to replace it again without know what is causing it to go bad. I put the new PCM in and it ran for one night. Then back to the same condition again.
The fuel pump does not run unless I jumper it.

 

[RonD]

The PCM runs most things by Grounding them.

Fuel pump is one of those things.

At the fuel pump relay there are 4 connections.
1. Fuel Pump Power, 12volts all the time, it has its own 30A fuse
2. Inertia switch wire, the above 12v is sent to inertia switch when relay closes(also sent to PCM to confirm fuel pump power is on)
3. 12volt replay power, this 12v comes on when key is on, 12v comes from EEC relay located next to fuel pump relay
4. Ground to close relay, this wire runs to PCM, when PCM receives 12v when key is first turned on it will Ground this wire for 2 seconds.

It reads like the Fuel pump relay is not getting the Ground from the PCM.
The PCM has several Ground wires(at the PCM mount point) that need to have good Grounds for the whole system to work.

This is a good page to book mark, lots of electrical diagrams here, the first page for 2.3l engine wiring shows fuel pump relay ground wire being light blue/orange and connecting to pin 22 on PCM.(also to the Jumper port)
http://www.therangerstation.com/tech_library/EDiagrams/index.htm

I would start with this info and see if that wire is good from pin 22 to the fuel pump relay, the Jumper port works and it uses that same wire to ground the fuel pump relay, this also means the EEC relay is supplying 12v to the fuel pump relay, so I would assume the problem is either in that splice point for the jumper wire connection or at the PCM end.

The year of the engine and wiring harness would be helpful if wiring colors are different.

Not sure if this will solve all the problems, but finding the issue with the fuel pump relay may point the way to fix other issues.

 

[rtamboli]

I have constant power from pin 22. Makes zero sense unless the PCM is bad. So I have power to all four sides of the fuel pump relay all the time, however the pump does not run.

I am not sure where to look. I just swapped out the PCM but with another used one and like I said it ran after that but then the next day it would not start. I certainly do not want to spend the money on another PCM unless I find what is killing it.

That wiring diagram is great is there a schematic of the inside of the PCM or documentation on trouble shooting that system. I know the GM shop manuals have a step by step diagnostic procedure but I have not seen anything like that for Ford.

thank you for taking the time to answer my questions you have been very helpful.

 

[RonD]

Well pin 22 is for pre-1995 diagram(OBD I), in 1995 - 1999(OBD II) they changed the PCM and pin 80 is the Ground control for the Fuel Pump Relay.

So as said it would be helpful to know what year wiring harness you are using.
Also what year PCM

A good source of wiring diagrams is also autozone repair guides:
Google: autozone ranger wiring

You should see the 1991-1999 wiring diagrams

As far as I know there is no way to home test PCM outside of 1 pin at a time, or hooking up an OBD I or OBD II depending on year, and seeing if PCM responds correctly

 

[snake]

You can send the pcm to ecmtogo.com and they can test it and repair it if its bad.

 

[rtamboli]

Welcome to TRS Rick~!

Probably not able to help you, but just to clarify, what year engine did you replace the 94 with, and did you get the wiring harness and computer from that vehicle?

Intermittent starts, in my experience, have been related to either battery or fuel delivery in most cases...but you didn't mention what the truck does when it doesn't start...does it just crank and not fire, or does it not even crank?

If it does crank, does it catch at any point and then die or does it simply not catch?

both engines are from 1994 Ranger the harness came with the new engine the components were all from my truck. I think that might the source of the problem in that the engine I bought did not have a camshaft position sensor. The mount hole for the CPS was blocked and never been used.

 

[rtamboli]

Well pin 22 is for pre-1995 diagram(OBD I), in 1995 - 1999(OBD II) they changed the PCM and pin 80 is the Ground control for the Fuel Pump Relay.

So as said it would be helpful to know what year wiring harness you are using.
Also what year PCM

A good source of wiring diagrams is also autozone repair guides:
Google: autozone ranger wiring

You should see the 1991-1999 wiring diagrams

As far as I know there is no way to home test PCM outside of 1 pin at a time, or hooking up an OBD I or OBD II depending on year, and seeing if PCM responds correctly

Well the engine harness came with the motor. But all the connectors were in the truck. I used the harness that came with the engine and just plugged into my truck that is when I found out there was no connector for the camshaft position sensor. The harness from my motor went with the core return unfortunately.
I am beginning to think the harnesses don't match and thus the brain keeps shorting out after a short period of time.

 

[zekew64]

I hate to say it, but you'll have to get another ECU. The reason why I say this is because the ECU you have is the California-only, that senses the cam sensor, while the engine you got is a non-California engine; ergo, it didn't come with a cam sensor, nor did the harness come with a cam position sensor.

The only fix, I think, would be to replace the ECU (main computer, inside cab, passenger side next to door).