Randomly will not start.

[tinman_72]

Hello fellow Ranger lovers. Over the last three weeks I have had an issue when I tried to start my '93 Ranger (4 cyl with 5 speed manual) on two occasions. Both times the engine would not start, it would only turn over for 5 or 6 seconds without starting. I would wait a little bit (a few seconds) and try again. The first time it started on the third of fourth attempt; the second time took quite a bit longer. When it finally started it was as if nothing was wrong. I turned the key and it started right up.
My fear is that this is going to start happening more often until it will not start at all.
Last fall I pulled the fuel tank and cleaned it out and put a new fuel pump assembly in, along with a new filter on the frame. Since the engine was being replaced at the time I also cleaned the lines and fuel rail out with carb cleaner and compressed air so I don't think I have a fuel supply problem. I also put all new sensors in. The only old parts under the hood are the EGR valve/sensor and the ICM.
I have check all the wiring connections under the hood and everything is tight. The only thing I can think of is that the ICM is going bad. It does have over 340,000 miles on it but I hate to throw $140 at it without being sure what the problem is.
Does anyone have an idea where I should start?

 

[RonD]

I would get a can of starting fluid(ether in a spray can).
Next time you have a no start, pull off PCV hose(or power brake hose), spray ether into intake, replace hose, then crank.
If it fires right up then fuel is the problem
If still no start then spark is the problem

One other test for a fuel pressure issue is the next time you have a no start, turn key off then on 3 times, this will cause the computer to turn on the fuel pump 3 times to Prime the system, then crank engine

You can test ICMs with a meter and some auto parts store have ICM testers if you bring it in to them.

I think you are right about the electrics, there is also the CKP(crank position) sensor, this sensor "tells" ICM and computer the crank is turning so "start the spark and fuel injectors", without this CKP pulse there is no spark or fuel to cylinders.
CKP sensors rarely fail, not never but rarely, and they tend to be dead or work 100%, so not intermittent, but the wiring could be.

 

[tomw]

Good answer and in addition, you can use WD40 as a fuel to check instead of ether. I am leery of ether being stored in a closed space, such as a truck cab. I'd trust a can of WD40 a lot more than ether.
One simple cause could be the relay for the fuel pump is getting worn, and makes intermittent poor contact, or that which powers the computer. Next time it fritzes, you could try giving a gentle thump to the appropriate relays, or check for power on the computer, and listen for the fuel pump 3-5 second 'prime' on key "ON".
tom

 

[tinman_72]

Thanks guys, that seems to be sound advise. I will listen for the fuel pump every time I try to start it until it happens again. I will also pick up a can of starting fluid and see what happens.
I work at the Zone and have the means to test it but since it is intermittent I think it will pass every time.

 

[tinman_72]

A little update. For a while there it was doing this infrequently but recently has gotten worse. It has gotten so bad that when I turn the key to the ON position the fuel pump does not whir for a second and the truck does not start. I spray starting fluid in it and it will start up and run fine.
I can jump #30 and #87 on the fuel pump relay receptacle and the fuel pump does run. I do not get a signal to kick on at the relay until the truck is started with starting fluid.
My first thought is that there is a bad ground or open somewhere but I don't think so because if that was the case it would randomly die after starting.
Any ideas?

 

[tinman_72]

No one?

 

[Kenneth S]

There is an inertia switch for electric fuel pump (usually mounted inside the cab on the firewall just below the heater box by where the passengers left foot would be) those things can give you fits when they go bad. Unplug it, and run a jumper wire across the plug to complete the circuit, and see what it does.

 

[RonD]

A little update. For a while there it was doing this infrequently but recently has gotten worse. It has gotten so bad that when I turn the key to the ON position the fuel pump does not whir for a second and the truck does not start. I spray starting fluid in it and it will start up and run fine.
I can jump #30 and #87 on the fuel pump relay receptacle and the fuel pump does run. I do not get a signal to kick on at the relay until the truck is started with starting fluid.
My first thought is that there is a bad ground or open somewhere but I don't think so because if that was the case it would randomly die after starting.
Any ideas?

Reads like the computer is not grounding the fuel pump relay with key ON, but does after engine RPM is above 500.
In Normal startup computer will ground the FP relay for 2 seconds then wait until RPMs are above 500 to ground relay again.

#85 and #86 on the relay is the 12v and ground to activate the relay.
12v comes on with key ON, this 12v comes from EEC relay
Check which one has the 12v with key on
The other one will be connected to pin 22 on the Computer connector, this is working since engine stays running, so you either have a bad computer or are not getting 12v at the FR relay when key is first turned on.
By "bad" computer I mean it is not grounding FP relay at key on, only after engine is running

 

[NIPs]

Next time u start it, turn it to the key on position, to see if the fuel pump is cycling, then start it after, and I bet it starts fine

Sent from my ME173X using Tapatalk

 

[tinman_72]

Next time u start it, turn it to the key on position, to see if the fuel pump is cycling, then start it after, and I bet it starts fine...

Sorry, I thought that information was in one of the older posts.

Sometimes the fuel pump cycles upon key on and sometimes it does not. When it cycles it starts just fine. When it does not cycle there is no signal to the relay and the truck does not start until I spray starting fluid. I can jump #87 and #30 and the pump comes on but it isn't enough to make the truck start. Once I spray it starts up and the fuel pump works fine.

I think I have tied the problem to humidity. Last time I posted we had several days of rain/humid cloudy weather and the problem existed every time I tried to start. Now the weather is warm and dry (relatively dry for The Southeast) and it has started every day with no problems.

I am thinking it is probably the computer. I may be trading for a '94 parts Ranger that is just like mine. If so I will swap them out and see if the issue improves.

 

[kimcrwbr1]

How old are the spark plug wires and plugs? You didnt mention a tune up plugs, wires, PCV, clean/change the EGR?

 

[Mark_88]

I had problems with humidity on most of my fords...moisture in general, actually. I solved this on my distributor vehicles by using the rubber boot from a Ford Tempo and have not have issues with it since.

Coil packs may generate a bit more heat than a distributor, but if you can put some thing over them (I know I will do this when my Ranger is finally converted to FI) see if it makes any difference...but, of course, if it is actually something else and you change more than one variable (such as replacing other parts) it clouds the real solution.

Another test would be to try starting it in the dark (really dark) and pop the hood...see if you have a bit of a light show with spark arcing then you may want to try a silicone spray on the wires...maybe even the coil pack...and may need to move the wires around to separate them from metal surfaces.

 

[NIPs]

Ur coil packs maybe cracked, or ur ignition module may be starting to go

Sent from my ME173X using Tapatalk

 

[tinman_72]

The problem is not spark. It fires up when I spray starting fluid. I have confirmed that there is no fuel because the fuel pump relay is not always activated.
The plugs, wires, PCV, fuel filter, fuel pump and all sensors are new since I finished refurbishing the entire truck back in October.
Another development: I rented a fuel pressure tester. When I turn the key to on and the pump cycles the fuel pressure only builds up to about 7 PSI. It is supposed to jump up to 35-45. I can cycle the pump 4-5 times and it will build up. With the engine idling the pressure is 30 PSI (is supposed to be 25-35) and when I disconnect the FPR it jumps to 40 PSI (is supposed to be 35 to 45). I think the filter may be clogged so I will replace it. If that doesn't help I will go on to replacing the pump which is still under warantee.
But here is the thing... this doesn't affect the original problem that the relay is not receiving a signal.

 

[RonD]

For the engine to stay running the Fuel pump relay would have to be on(closed).

Here is the EEC-IV connector diagram: http://www.auto-diagnostics.info/ford_eec_iv
Unhook battery's ground cable before removing the EEC connector, then hook it back up for testing.
Do NOT forget to unhook it again to reconnect EEC.

Pin 22 should have 12volts when key is on, the 12v comes from the EEC relay, it passes thru the Fuel pump relay's coil and to Pin 22.
The computer(EEC) grounds pin 22 internally which causes the coil to become a magnet, closing the relay, this sends power to the inertia switch and fuel pump.