94 intermittent crank but no start

94 explorer limited, 90k. cranks but wont start, had towed twice and
garage says when they get it back it starts fine. No codes tripped.
After reading some older postings, the next time it didn't start, i
tried switching the ABS and Fuel pump relays. The engine cranked for
about 5 seconds and sputtered, but didn't start. I had a friend crank
while I gently wiggled the power box that contains the relays, and it
started. I took it home and un-bolted the power box and did not see
anything obvious inside or with the harness coming in or going out. I
sprayed WD-40 on the underside of the power box and 2 break out
connectors near by, then blew dry with compressed air. It started last
night and this morning, which means nothing, but I was wondering if
this might point someone to the source.
I have replaced nothing, other that a fuel pump last year due to a
rusted/leaking top tube.

Rich wrote:
> 94 explorer limited, 90k. cranks but wont start, had towed twice and
> garage says when they get it back it starts fine. No codes tripped.
> After reading some older postings, the next time it didn't start, i
> tried switching the ABS and Fuel pump relays. The engine cranked for
> about 5 seconds and sputtered, but didn't start. I had a friend crank
> while I gently wiggled the power box that contains the relays, and it
> started.

The fuel pump relay is the usual culprit. Try swapping the A/C relay
with the fuel pump relay. These relays have two sets of contacts. The
A/C and fuel pump use different sets of contacts (the A/C uses the
normally closed pair, the fuel pump uses the normally open pair) so the
unused contacts will be like new.

There are also other relays there for the ignition/computer, could be
one of those. Try swapping with other relays of the same part number.

Have someone crank it a bit, then immediately check to see if you have
fuel pressure at the fuel injection rail. There is a schraeder valve
there for that purpose. There's a safe procedure for doing that
somewhere, and the pressure specs, but in general you don't want to do
it WHILE cranking or have a cigarette dangling from your lips. It's
under pressure and will spray out. If it doesn't, you'll need to figure
out why. There's the relay, fuse, and wiring to the pump, the pump, and
the fuel pressure regulator. The filter is unlikely as that would cause
problems with high fuel flow, not just starting.

Starting requires spark, the proper fuel/air mixture, compression, and
timing. The last two are not likely to cause intermittent starting, so
focus on the first two.
Good luck.
-Paul

Another possibility is the crank sensor. It is a sensor mounted on the
front of the engine behind the cranshaft pulley( I think). It senses
position of the crankshaft and sends this info to the computer for
proper timing and spark. If its defective, the car will not start. Try
wiggling the wire connecting to the crank sensor.
Do a search on "crank sensor". A bunch of people had problems with it
like you. I do not know if there is a way to test it or not.

Mikepier wrote:
> Another possibility is the crank sensor. It is a sensor mounted on the
> front of the engine behind the cranshaft pulley( I think). It senses
> position of the crankshaft and sends this info to the computer for
> proper timing and spark. If its defective, the car will not start. Try
> wiggling the wire connecting to the crank sensor.
> Do a search on "crank sensor". A bunch of people had problems with it
> like you. I do not know if there is a way to test it or not.

The crank position sensor affects running as well as starting. I would
think it would be dying and running poorly, not just cranking without
starting. Here's some good info from Dr. Bob on the crank position
sensor:

"The crank position sensor is the hall effect sensor pointing to the
front of the crankshaft. The hub behind the front pulley has grooves
machined in it, with one groove missing. the sensor reads each of the
pulses from the grooves to know exactly how far the crankshaft has
turned, and reads the missing groove to re-identify a known position
to reference from.

This allows the ignition and fuel injection systems to make sparks and
fuel at the right time.

There is a 'limp home' mode, as you have discovered, that allows the
engine minimum operating ability so you aren't stranded.

A failed sensor generates an error code, so the diagnosis is fairly
straightforward. If you weren't at a Ford dealer, the $200 is the
result of not having the right code reader. The sensor takes mere
minutes to change."

Here's a description of the problems it causes:

"The crank sensor went out last fall on our '92 XL, too. The car would
suddenly die and wouldn't start again. After about 10 minutes, it would
start up fine and run like there was nothing wrong (until it would die
again, usually days later). Finally, it would run only poorly (the
"limp home" mode, I guess)."

I have a 91' 4.0 liter Ford Explorer (176k miles) which is having a
similar problem in that it has trouble starting at times. My radiator
coolant levels are going down little by little and I have to keep
topping it off. I'm suspecting I have a blown head gasket, I pray it's
not a crached head! I might tear into that project after the 1st of
the year. Is this a symptom of yours too?

RobJea wrote:
> I have a 91' 4.0 liter Ford Explorer (176k miles) which is having a
> similar problem in that it has trouble starting at times. My radiator
> coolant levels are going down little by little and I have to keep
> topping it off. I'm suspecting I have a blown head gasket, I pray it's
> not a crached head! I might tear into that project after the 1st of
> the year. Is this a symptom of yours too?

The starting problem is most likely the fuel pump relay. It's under the
hood on the passenger side of the engine bay, with the fuses. Swap your
A/C and Fuel Pump relays, see if that fixes it.

Coolant leaks are commonly caused by the radiator, heater core, and
intake manifold gasket. The head gaskets will go if you overheat it,
though, so be sure you don't let it go that far. If it's a very slow
leak, stop leak should easily fix it.
-Paul