96 Explorer 4.0 OHV V6 suddenly dies- changed relays

[1karkrazyguy]

I have a 96 Explorer 4.0 OHV V6, 170,000 miles, that has twice suddenly died at random times when driving on surface streets the last 2 weeks. Truck died on me today after driving half a block. Engine just suddenly cut out, quit, would not immediately re-start, starter cranked fine, no problem. No DTC codes being thrown at all when checked.

I opened the hood, opened up the under hood fuse box, swapped the relays for the fuel pump & the PCM and the truck started right up.

I bought a new set of relays at Ford as they were all 16 years old and relays are mechanical switches / contacts that wear out over time and usually do it when it is extremely cold or hot.

That COULD possibly mean problem solved. Will have to drive truck tomorrow again.

But there are the following maintenance issues I have to do the next 2 weeks:

1. Truck does have issues with upper & lower intake manifold gaskets leaking, losing coolant through a leak at the front above spark plug hole #4 and at the rear of the engine, passenger side, dripping on the exhaust manifold.

2. the valve cover gaskets are leaking, oil dripping into spark plug holes. i have new FelPro gaskets for them.

3. a rough idle at start after sitting overnight that smooths out after a minute. I am getting ready to replace with all new OEM Ford upper & lower intake manifold gaskets, along with a set of 6 new Bosch fuel injectors and a new OEM Ford fuel pressure regulator and fuel filter.

4. For regular maintenance, I have in the last month installed all new Motorcraft iridium plugs, all new Ford spark plug wires, new serpentine belt, tensioner, fan clutch & OEM Ford fan and 3 new O2 sensors, and a NOS oem Ford coil pack, and a new water temp sensor for the PCM (Powertrain Control Module- the computer that controls the engine & automatic trannie.) as they all had 170k miles on them.

5. All engine management sensors have been changed gradually over the last 5 years as they have slowly failed.

6. Oil change with filter, cleaned the MAF sensor with Radio Shack electronic parts cleaner, no residue.

Truck is 2WD, with a recently rebuilt automatic.

I'll post how it all sorts out. I know the intake manifold gaskets, new fuel injectors, fuel pressure regulator & valve cover gaskets will make my engine and me very happy-

[Dono]

Original fuel pump?

[vroomzoomboom]

Originally Posted by Dono

Original fuel pump?

x2. if the truck dies again. turn the key off, then on again, but not to the start position. you should be able to hear either the fuel pump cycle for about a second or two.

[1karkrazyguy]

Thanks for the reply Dono, vroomzoomboom. Much appreciated.

I had the oem Ford fuel pump replaced when it died 50,000 miles ago at 120,000 miles, which is about normal for the Explorers, along with a new fuel filter.

The fuel pump is cycling, heard it when I did do the key on test.

I replaced with new Ford relays, the relays in the under hood fuse / relay box on the drivers side by the fire wall, the fuel pump and engine control module relays. Relays wear out with age and start to fail intermittently when there are extremes of heat and cold as they are a mechanical switch, with electrical contact points.

On a side note related to this problem, the 90's BMW's straight 6's & v8's would do this when they hit 90k to 110k miles, where all power to the engine computer cut out on long or short trips, when the engine was running and the dealership and my independent mechanic could not figure it out what was wrong with why these cars, that would be running fine one moment and then the transmission failure light would come on, and the engine would not fire while the starter motor cranked and the BMW diagnostic computer could not get any info from the car's engine computer in diagnostic mode.


That should have been a BIG HINT to the service techs, BUT they are not MECHANICS.

Service techs just replace parts in an attempt to fix a problem....


The BMW automatic transmissions were the GM designed 4 speeds that they have used for the last 40+ years here in the USA with a BMW custom solenoid throttle body on it, and made under license in France. It has a GM sticker on it as well....

The dealerships, independent repair shops made fortunes on selling rebuilds or new transmission, engine and transmission computers at $700- $1200 a piece, etc. not fixing the problem and sending the customers off, problem unsolved !

I happened to stop in one day when my mechanic was going nuts with one car, telling me he had spent a fortune with a car, with replaced engine computer 2x, transmission computer 2x and was thinking of having the transmission rebuilt... I asked him if he checked for shorts in the power circuits, bad battery, etc...

He said everything was ok with electrical, no shorts. I asked him what the symptoms were and then I took the good relay from my BMW that supplied power to the engine computer and swapped it out with the engine computer relay in the car that would not start, that had a " bad transmission indicator", that he was trying to fix.

The car fired right up, no transmission failure light, BMW Modic diagnostics tool could access the engine computer now. There were NO DTC codes in the engine computer of the loss of power/power failure of the relay.

No power to the engine computer, that means computer is not storing any DTC's... It had no power to do so...

I put the bad relay in my car and my car would not start, transmission failure indicator lit up on the dash.

My buddy and his shop has made a killing " fixing " these cars, even for the local BMW dealers as they don't know how to work that well on ' legacy cars ' as they like to call older models... The relays are $16 dollars...

Back to my Explorer- going to get my meter out, check all the ignition systems components / controls, section by section, and then I am going through the battery connections tonight, cleaning them and installing the new oem coil pack.

I hope to do the upper & lower intake manifold gaskets, new fuel injectors, new fuel pressure regulator, over the holidays.

I will post what I find is the solution to the sudden stalls, after I do all intake manifold gaskets, etc.

Happy holidays-