The first thing I would do is the next time it does not start spray some starting fluid down the throttle body and see if it runs or at least fires a bit. This will tell you if you have spark or not.

Does not run, no spark. Try replacing the coil.

Does run some, no fuel. This motor should have a pressure sensor behind the distributor to stop the fuel pump if there is no oil pressure (safety thing). You should also have a fuel pump relay that should start the pump for a few seconds when the key is turned. Back around by the brake booster is a plug that you can jump to power the fuel pump.

A fuel pressure tester gauge would help in all of this too.

 

Open the gas fill cap.

 

Thanks for the replies!

OK, maybe I should say a little more about what I've done. In March when it started becoming intermittent, I had my daughter turn the key and I looked in the throttle body; the fuel injectors weren't shooting any gas. I tried to dump gas down the throttle body with no luck, it didn't try to fire. Then I went and bought a spark tester that goes between the spark plug wire and the plug and found I had no spark. That made me think maybe the ignition control module(?) under the distributor cap. I changed the rotor, distributor cap, and ignition control module but it made no difference. Those parts are good, it ran good yesterday until I shut it back off in my driveway.

A friend at work said my fuel pump might be dead or weak. I jumpered the fuel pump relay and can hear it running and the pickup runs strong when it does start. I would test the fuel pressure but that's not easy on a 1995, they don't have pressure test ports so I'd have to remove the fuel filter again. To clear up any concern about the fuel filter, it probably has less than 300 miles since I changed it. Who knows, maybe it is a bad fuel pump but would that cut out the spark too? I'm hoping it's not a fuel pump because it's got a full 34 gallon tank that would need dropped.

I removed the gas cap completely and it didn't make a difference. I hear the fuel pump for about 3 seconds when the ignition is turned to on. It turns over fine but just doesn't fire....again.

 

Swap out the coil.

 

OK, now it has a new coil too. It turns over fine but no spark according to the cheap Harbor Freight inline spark tester. It was getting dark but I assume it also isn't getting the injectors to pulse and send fuel. I put it back on the charger for the night.

 

Well hell....

You have now replaced all of the ignition parts. If I remember correctly (it has been a long time) there is no other computer/sensor control on your 95 motor ignition system.

Need to get a wiring diagram and start testing and tracking the wiring.

 

If he can reliably replicate with ambient temp it seems odd that it'd be wiring.

 

Very true but he has replaced all of the ignition parts. The control module on the distributor could be bad??? I don't remember a test for them.

 

start by verifying that you have 12 volts on the pink wire at the coil while cranking.

Thanks Tom

 

does the check engine light function normal- turn key on- light is on for 1 sec, off for 1 sec, then on solid until start?
this is the computer self test

Thanks Tom

 

Thanks again for the responses. Yes, it still seems temperature dependent. Yesterday it wasn't starting and it was in the 40's. I came home after work and it's 36 degrees and it's now started three times in a row. This is after it wouldn't even start (or fire) once during summer.

Larry- I have changed the ignition control module in the back/under the distributer cap.

Tom- I just went out and got a video while I turned it to the on position and then started it. The check engine comes on for maybe a second, flips off and then back on quickly, then stays on until I start the engine and it shuts off.

Tom, I was also wondering if I had power on the coil (or anywhere) when I try to start it and it's not working. I've had cars in the past that lost the accessories function while they were running and you'd have to wiggle the key a little to get the gauges to work again. Do you think it's possible that I'm losing the "on" function when I twist the key forward to engage the starter? Maybe the ignition switch is going out? Thanks for mentioning the pink wire on the coil because I haven't found myself a good wiring diagram.

Someone also mentioned an oil pressure shut off that disables the gas and spark if there's no oil pressure? Is it possible that's bad and causing my problem? I would have more oil pressure on startup with colder oil. Maybe I shouldn't have put synthetic in it.

 

correct check engine light operation is great. the system has power and there are no issues with the sensors (completed self test). Indicates the system is not being triggered. You have already changed the ignition module, so the next step is the trigger coil in the distributor (intermittent- heats up and looses contact internally). replacement requires disassembly of the distributor- if you are not comfortable doing that, replace the distributor with a reman unit

Thanks Tom

 

the oil pressure switch on these trucks is a parallel circuit for the fuel pump- does not shut the engine off for oil pressure issues.

Thanks Tom

 

Thanks for letting me know that the oil pressure doesn't kill the starting circuit. I'm working twelve hour days the next couple days so this will need to wait until the weekend. I'll look into changing the trigger coil or hit the junkyard after work and get a whole distributor. I think I can swap the distributor and get it back in the right position.

 

OK, so it was cold again today and I still thought the problem might be in the ignition switch. I started the pickup (it's in the upper 30's) then drove about 10 miles to my brother's house and gave him a ride. Afterwards we were sitting in front of his house talking and it just died like I'd turned the key off. It turns over fine but it's back to no spark, no gas. We got his meter out and I tested the pink wire on the coil, it has 12.5 volts in "run" position and 10.5 while it's cranking over. That rules out the ignition switch. If it starts tomorrow morning, I'll probably drive it home and then go buy a used distributor this week after work. It definitely doesn't seem to be getting the signal to spark and fire the injectors.

 

Apparently it was the ignition pickup coil in the distributor. It was snowing this morning and the pickup still didn't start. I'd watched some YouTube videos and decided to just go to Napa and buy a new distributor rather than getting an old part from a junk yard. After installing the new distributor the truck started right up and I drove home. I still need to get the timing adjusted but it's running again and I think it's all good. Thank you again for all your help on this!

 

thanks for following up.