Mazda truck stalling, not re-starting

[Clint]

Hey guys, I’m new to posting on the forum, but have been reading for some time.

I own a 1994 Mazda B4000 LE 4.0 V6 pickup truck, runs nicely, & in pretty nice condition. But lately my check engine light has been staying on and the truck isn’t like normal. I’ll be driving it and park, run my errand, come back to start it and it starts, sounding like its a cylinder down. After a few hard revs it will go back to normal though. I’ve checked my plugs, wires, and all the basics & they all seem fine.

Every once in a blue moon I will be driving along, and all of a sudden it just dies, I pull over, park it, and try to re-start it, and nothing. It just keeps turning over. After about 10 minutes or so it will finally re-start though. This has happened about three times, and have all been in different scenarios. It’s happened sitting while idling, once going down a hill, and once with my foot on the gas. I also added half of a can of SeaFoam to my full tank of gas, and the other half of the can directly into the vacuum system to clean the injectors and such. The guys at O’reilley auto parts told me that this could possibly be a coil pack issue?

And lastly. There’s been a few occasions where I’ve driven it for awhile, come back to start it, and it turns over with no fire. Ill leave it sit for a hour or so, come back, and it will start right up. i think I’ve narrowed it down to possibly the fuel pump. Sometimes you hear it prime when the key is turned in the on position, and of course it will then start. But when it doesn’t start, it also doesn’t prime.

With all these problem happening at once its hard to figure out what the actual problem is. What do you guys think? Where should I start, and focus all my time?

Thanks in advance,
Clint

Topic

[college man]

Start with having the code read and posting the code.
Then we will help from there.

[Darren]

Yes it would help if you got the code read, sounds like its a fuel problem. The pump might be starting to die, might explain why it runs poorly for a few seconds when starting, and might also explain why it stalls every so often.

[Bill]

There are a few things that come to mind but I think you’re on the right track with a failing fuel pump. Could also be a plugged fuel filter but not likely.

If you don’t have a fuel pressure gauge and a helper when it’s acting up it will be hard to diagnose it correctly, but you could check the pressure anyway.

I believe it should be around 35 psi.

If there is no spark when it quits it could be a bad ignition module.

[dreamer2355]

Next time it stalls and doesn’t restart, check for fuel and spark and see which one is missing.

Keep us posted.

[Clint]

Sorry for the delayed response.

I went to two mechanics here in town and they told me they did not have the equipment to pull the codes, as its “Pre ObD2”. I’ve been searching the Internet & reading a Chilton front to back looking for a way to pull these codes by myself.

It stalled again today and after I got it home I decided to look into the simple fixes, before going drastic. I focused my attention on the fuel pump relay, under the hood. Tested it, and it didn’t always come back with continuity. So before replacing it, I wanted to be 100% sure it was bad. Later on my truck just wouldn’t start. It would crank, but not start. So I swapped the relay for the fuel pump with the headlights. And what do you know? It started! Swapped them back to original, and it didn’t start!

On a related note – the filter was a tad clogged, so I replaced that.

So what do you guys think? Could this relay have been the cause the entire time?

Thank you guys, you truly have been great support.
Clint

[college man]

I would suggest the relay is a great possibility.
keep us posted.

[Bill]

I think you found the problem.

[Clint]

Relay wasn’t the problem. Replaced it today and was good. No stalling as of yet. But just went to leave and the truck wouldn’t start. It cranks but no start. I’m completely baffled. I’m almost starting to believe there may be a short somewhere from the fuse box to the pump? Or from the fuse box to the wiring harness?

By replacing the relay my check engine light doesn’t come on immediately like it was, but it does after a few miles of driving. Do any of you happen to know how to pull the codes without a reader? Such as the jumper method? I followed Eric’s video on it (http://m.youtube.com/watch?v=8M5BaAa6tCM) But the method is for honda’s. there isn’t that plug under the dash on my truck as it was on the Honda. I guess there are not any mechanics around here that have OBD1 readers, and both auto parts stores don’t carry them.

Also, when I turn the key to the on position, should I be able to feel that relay click? I’m not feeling a click or hearing any sound. The fuel pump isn’t priming either, which is why I’m starting to think about a short in a wire.

Thanks,
Clint

[Bill]

Alright, I did some checking I have info on your truck but I need to print it off and scan it to post it here. That truck basically uses ford components. It’s called EEC.

Now that the cob webs are falling out of my ears something rings a bell with that system.
The EEC power relay was a common fault and when it fails it won’t turn on the fuel pump relay.

The EEC power relay that’s located under the hood to the rear of the battery, looks from the pic I have it’s beside the fuel pump relay. There are 3 relays together there. I think that relay could be the problem.

Also, you should be able to retrieve fault codes with an analog volt meter hooked to the diagnostic connector and the ground pigtail there, but it’s a pain in the butt to do.

[Clint]

Yes I saw the EEC relay in there. Tested it & as the fuel pump relay was, it doesn’t always come back with continuity. I’ll have that replaced within the hour. Could that be the main problem?

And yss, the Chilton said I could pull the codes with the meter, which I have. I just have no clue on how to do that.
Thanks

[Bill]

There are so many things that can cause your problem it’s crazy. I can only explain through experience the areas that are common to failure. Ford used those crappy relays for many years. Fortunately they are not expensive.

I don’t think either one of those relays will set a fault code.

Check this out for test procedures….https://www.youtube.com/watch?v=ZY9BeHFW1ng

There are similar videos there too.

[Clint]

Replaced the relay, and so far so good! Drove it for 10 minutes or so and no stalling. Parked, shut it off, and it started. Will let you guys know what happens in the upcoming days.

Thank you, you have truly been a help!
Clint

[Bill]

Let us know how it works out, Clint.

[Clint]

Alrighty. Pulled the codes & came back with a 03 & 17. Which are Distributor (G1) & Heated 0xygen sensor.

[Bill]

I would disconnect the battery for a few minutes to erase those codes and see if they return. Since both the ignition and o2 sensor heater rely on the EEC Power relay to operate the codes may not return if the relay was bad.

If they do return then we can deal with them for you.

[Author]

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