How would I go about diagnosing this problem (non TD but should be simple)

[big_P]

I bought an 88 Mercury Grand Marquis "Blue Bomber" and it has the 5.0L torque monster. Great winter car choice, huh? Oh well.

Anywho, it seems that the starter struggles to spin the motor. I did a Battery, starter, and alternator test by a VAT-45 machine at school and they all tested fine. I'm going to be replacing the battery anyway because it's starting to get cold and I've learned not to trust NAPA batteries.

What's my best way of diagnosing the problem? The cables aren't bad but you can tell that they're from 1988. I would suspect the starter itself, but I'm not sure.

I can leave the lights on for ten minutes and usually not have a problem. If I'm driving at night with the lights/heater on, it'll turn over slowly. Tonight, I made a quick run to the gas station after getting coffee with a friend, and the car did not have enough juice to start. I didn't even leave the lights on while I was pumping gas. It almost sounds like an intermittant problem, but the "amp" light has yet to come on.

Any ideas would be greatly appreciated.

Thanks,

Pete

[big_P]

Forgot to mention that I did a parasitic draw test and came up with nothing.

[flatlander757]

What were the CCAs that the battery was cranking out for the test?

I'd say it may be the alternator starting to kick the bucket... just too early for the machine to pronounce it dead.

You have any green stuff growing on the battery terminals, starter or alternator hook ups?

[big_P]

I cleaned the battery terminals very good. It's an 880cca battery, it's no slouch. I'll do another test on the alternator.

[t2turbo600]

you bought a ford problem solved

[charger R/T]

Is this a standard package car (internal regulated alternator) or police package car (external regulated alternator)? Does the battery light come on with the key on and engine off? external regulated cars have issues with this. The wire that turns the light on breaks in the section of the harness that hangs from the engine to the drivers side fender. If it breaks the alternator sometimes won't charge and never turn on the light. Internal regulated cars also have this issue but happens much less.

Get your volt meter out and check voltage at the battery and at the alternator with nothing on but the engine then again with everything on. How much lower was it at the alternator with everything on then at the battery. In 86 ford stopped running the alternator wire right across the front of the engine straight to the solinoid (about 3 to 4 feet of wire) to running it from the alternator to the passenger fender to the header panel across the header to the passenger side fender to the solinoid (about 12 feet of wire) I have found many with voltage drops with this system. The fix it to get a new battery cable and run it from the alternator to the solinoid right across the front of the engine just like they did on the 85 and back cars.

The issues you describe sounds like it may have an alternator that can't keep up with the extra load you have at night or the cable issue I listed above. My guess would be the cable issue. Also internal regulated alternators were lower amp units then the external ones.
Tim

[big_P]

Charger R/T, I will look into that! Thank you very much.


I noticed that for a 90a alternator (I think it is), the output wires are SO small! I couldn't believe it at first. The ones on my 2.5L Chrysler were probably 4ga whilst these are more like 10ga.

[charger R/T]

If its a 90 amp its internally regulated. The external ones were 100 amp (up from 70 in earlier models) and much larger in size.
Tim

[big_P]

I kinda assumed it was a 90. The tag had worn off, but the alternator produced 83a at ~2000rpm (no tach).