'87 Ranger Won't start, has spark and fuel

[neggen32]

Hey guys! I'm completely stumped on why my Ranger won't start right now, I've read all the threads about this problem but I think it may be something unusual. I drive an '87 Ranger with a '91 4.0 swap.

A few days ago I was sitting at a red light and the engine cut off and wouldn't start. It had been running perfectly fine before this. Thinking I ran out of gas, I put more in and it still won't start. I've checked just about everything I can find and this I what I know:

-Battery is charged and starter cranks strong
-Has spark, will start up and run for a few seconds with starter fluid but dies after that.
-Fuel pump primes and squirts fuel when ignition comes on
-Fuel pump is getting 12V
-Inertia switch has been reset
-Fuel pump relay has been replaced with new one
-Fuel pressure test on fuel rail is good, at 35 psi.

What else could be keeping it from starting? Thanks in advance for any ideas!

 

[RonD]

Welcome to TRS

Reads like fuel injectors are not opening.

Quick test would be to crank cold engine a couple of times and pull a spark plug or two.
Spark plug tips should be wet with fuel.

If not then try this first, on the upper intake where the air tube from air cleaner connects, passenger side, is the TPS(throttle position sensor), it has 3 wires connected.
Unplug this 3 wire connector and try to start engine.

TPS send computer .9volts if throttle is closed and above 4.5volts at wide open throttle(WOT).
Computer has a Clear Flooded Engine Routine, if computer sees WOT voltage from TPS before you crank the engine it will not start fuel injectors so no fuel.
If TPS should short out..................
East test so try that out first

Next would be to test for voltage at the injectors.
Each injector will get 12volts when key is turned on, the red wire, it just daisy chains from one injector to the next.
Test for 12volts, both wires at each injector should show 12volts, an injector is just a loop of wire.

Computer Grounds each injector to open it, but 1991 4.0l will have Batch Fire so 3 injectors share 1 Ground wire back to the computer.
You need a Noid Light plug into one injector to see if it is being Ground, test light often won't work because Ground is only on for milliseconds

 

[neggen32]

Thank you for the reply! My multimeter stopped working yesterday so I was unable to do some of those tests, but my friend had a new TPS in the box, I replaced the old one and it's still not working.

I'll have grab a new multimeter and test the fuel injectors. I don't know why they're not opening

 

[RonD]

So spark plugs were dry?

The 1990-1994 4.0l used an EDIS-6 module for spark.
It uses the Crank Position(CKP) sensor to time spark, and it also connects to the Coil pack.

It also has 2 wires that go to the computer(3 if you count ground wire)
1 wire sends the computer the timing pulse from CKP sensor so computer can time the fuel injectors, no pulse = no injectors.
Since spark works, adding fuel starts engine, then CKP sensor is working and so is the EDIS-6 module, but maybe the wire going to computer is the problem.

Check the connector on the EDIS-6 module, pin 1 wire is the PIP, signal the times injectors

 

[neggen32]

Yes, spark plugs were dry. Sorry, just saw your message!

After testing everything I could think of, I gave in and had a mobile mechanic come out and look at it. He charges 60 bucks for a correct diagnosis, so I figured it would be worth a shot. He took a look at it and was all bent out of shape about the fact it had an engine swap, said it would be hard for him to pull codes or do any troubleshooting. Weird.

But he did say that he's seen similar issues hundreds of times, and his first instinct would be to replace the ignition module and go from there.

But then I was thinking the same as you, if it's getting spark then the ignition module can't be bad right? I'll try to find the wire you're talking about and check that. Thank you!

 

[little red ranger]

Buy ,borrow from autozone if they have one or steal a noid light,,, this will tell you if the injectors are firing,,,, the computer grounds the injectors to make them fire,,, the computer does this on my 99 via a signal from the camshaft position sensor which sets on top of the camshaft schyoronizer ,,, not sure where your signal comes from on a 87 or should I say 91,,, but no signal no injector squirt,,, I think you get where I going,,, good luck

 

[neggen32]

Ugh, so the mobile mechanic I hired eventually gave up, and I had to get it towed to the nearest reputable shop. The mechanic there seems really knowledgeable and has actually owned a few 80's Rangers himself. He confirmed that the injectors aren't opening, apparently they are getting power but no signal. After trying to chase down the problem for a few days, his only guess was to try replacing the truck's computer. What do you guys think of this? Where would be the best place to find a computer?

 

[little red ranger]

Ok I got what i am about from another site for a 86 ranger so your 87 might be the same,, I am going to do this inn 2 posts hope the information helps--------------------------- The 86 was the 2nd year that EFI was available. It does not have a cam position sensor. The injectors fire in 'banks' of 2. #1 & #4, #2 & #3, with the injected fuel 'sitting & waiting' for the intake to open for 1/2 of the cylinders.
I do not remember the injector timing being done by anything but the computer, using the distributor as a 'go' signal.
The injectors will be disabled at WOT with the engine running at 0 rpm.(clear up flooding)
The fuel rail is charged with fuel by the short 'on' cycle of the pump at key ON. The computer monitors oil pressure(IIRC) to re-enable the pump after the engine starts.
If you don't have fuel, have you checked pressure & flow? Do the injectors 'tick' at all? Have you used 'noid' lights or a probe to determine if the ground pulse is there or not?
Have you checked the 'rollover' switch? Does the pump run?
Do the simple tests that are quick and easy, and most likely before jumping to a computer as they actually rarely fail, FWIW.
tom
_____

 

[little red ranger]

Without a lot of thought, yes. It could also be the TFI - thick film ignition - wiring back to the computer as that's the source of the timing & running signals. The PIP signal tells the computer 'you are on cylinder #x and it should fire any ms now' sort of. I really don't have it in memory to call up as it is so stable a system that you do not run into problems often.
You could take the TFI to parts stores in the past for testing, or can test if you know the procedure, with jumpers and a VOM, IIRC. The SPOUT is used to set or release computer timing vs fixed. When the SPOUT jumper is removed timing should be at 10BTDC fixed, warm engine. Some TFI have a start circuit that does two things, or maybe they are two different circuits. One allows push starting, and the other supplies more coil voltage for starting rather than stepped down voltage for 'running'.
tom ------------------- I dont think your computer is bad,, but if it is and you have to get one here is where I got mine --- Flagship One Inc. 21 Ryder Pl East Rockaway NY,,,Had to give them some info so they good build it for my truck,, it failed there test and they had to rebuild me another one and express shipped to me to make up for the delay,,, oh and it has a lifetime warrenty and they beat almost everyones prices !!!

 

[little red ranger]

In simple terms your distributor tells the computer to fire the injectors via the TFI,,,,, I think,,, I believe that is what the above tells us,,, so have your mechanic to check the TFI and the wires going from the distributor to the TFI and the wires from the TFI to the computer,,, hope this helps

 

[neggen32]

I really appreciate all the advice you guys have given me! Unfortunately it's gotten a little more complicated though. After buying a new computer at the mechanics request, they eventually figured out the problem wasn't the computer, but the "PIP signal to ECU was grounded with the key off". The thing is, the previous owner who did the engine swap used a 1991 4.0 everything, except for the wiring harness going from the engine to the computer for some reason. This is still the original 1987 harness, with tons of ugly splicing and things not matching up. We don't know why he did that, or why it ran so well until all of a sudden it didn't. The mechanics ran a new wire around this harness and got it to start, and unplugged a few sensors (TPS and one other one I think) because they said it ran better with these unplugged. I went to pick it up today and I couldn't even get it out of the lot, it just kept dying when it got any gas and sounded terrible.

They tried to tell me I could feather the clutch and try to keep the RPMs up to get it home but I said I wasnt comfortable doing that and I don't really consider it fixed yet. They said the only permanent fix is to get that 1991 wiring harness, along with a MAF and intake that can accept one. Where would be the best place to find these? What are your guys thoughts?

 

[Ty S]

A pick and pull/ scrapyard?

Sent from my Nexus 6P using Tapatalk

 

[RonD]

I really appreciate all the advice you guys have given me! Unfortunately it's gotten a little more complicated though. After buying a new computer at the mechanics request, they eventually figured out the problem wasn't the computer, but the "PIP signal to ECU was grounded with the key off". The thing is, the previous owner who did the engine swap used a 1991 4.0 everything, except for the wiring harness going from the engine to the computer for some reason. This is still the original 1987 harness, with tons of ugly splicing and things not matching up. We don't know why he did that, or why it ran so well until all of a sudden it didn't. The mechanics ran a new wire around this harness and got it to start, and unplugged a few sensors (TPS and one other one I think) because they said it ran better with these unplugged. I went to pick it up today and I couldn't even get it out of the lot, it just kept dying when it got any gas and sounded terrible.

They tried to tell me I could feather the clutch and try to keep the RPMs up to get it home but I said I wasnt comfortable doing that and I don't really consider it fixed yet. They said the only permanent fix is to get that 1991 wiring harness, along with a MAF and intake that can accept one. Where would be the best place to find these? What are your guys thoughts?

This doesn't make sense if, as you said in first post, "it was running fine"

If there are alot of splices then at least one has failed, so engine died.

The 1987 2.9l used a Speed Density computer software/firmwear which used a MAP sensor as the main air:fuel mix baseline.
2.9l also used a distributor with TFI spark system.

4.0l engines never used this, they used Mass Air Flow computer software/firmwear that used a MAF sensor as the main air:fuel mix baseline.
And were distributorless, they used an EDIS-6 module and Crank Position sensor for spark.

So you already have MAF sensor or 4.0l computer wouldn't have worked.
The PIP on the 4.0l comes from EDIS-6 module and yes, if that wire was not working then fuel injectors would shut off but spark would still work, and so would fuel pump.
PIP is the timing signal for spark and fuel injectors, EDIS module gets it from Crank sensor and uses it for spark, and passes it on to Computer.
Computer also sends back a recommended spark advance or retard signal to EDIS module to make engine more responsive to driver input.
Spark would still work without computers return signal, engine would just be sluggish because spark advance would be delayed.


Wires are wires, as long as they are connected correctly the year or model of harness wouldn't matter, since both are EEC-IV 60-pin computers.
Using 4.0l wiring harness with 4.0l computer would make wiring easier but a 2.9l wiring harness could be used.
There are not that many differences
ECT sensor, engine coolant temp << same on both
IAT sensor, intake air temp << same on both
O2 sensors << same on both
TPS<< same on both
IAC Valve, idle air control << same on both

MAP sensor or MAF sensor << different
TFI module or EDIS module << different

So outside of sensor connector mismatches there are only a few wires that need to be changed

For dead engine while driving there are only a few wires that can do that.
12volt power to computer and/or engine systems(fuel injector power or spark power)
Crank position sensor wires to EDIS module(where PIP signal comes from)
PIP signal to Computer from EDIS module