meppwc

My 92 F150-4.9 cranks very slow at startup. Had the battery checked and no dead cells and cranking amp @ 650. What else would cause a very slow cranking? It does startup with no problem but concerned with the slow cranking. Is there a possibility of a starter going out that would cause that, or anything else?

Steve83

#1 most-likely cause: battery terminals. Click this & read all the captions:


(phone app link)

Next most-likely: all the OTHER terminals on the heavy cables:


(phone app link)

If it's not already there, the bottom end of the negative cable should be on the lower starter mounting bolt, and that part of the starter casting should be clean & shiny.

If it's still slow after all that, try to check the starter draw. It takes a special inductive clamp meter, like this:


(phone app link)

It should be ~140A DC. If it's significantly higher, the starter motor may be dying. The MC reman PNs are in the next caption. If it's lower, the starter solenoid switch (on the starter) may be burning out.


(phone app link)

If you can find a replacement solenoid, it's pretty easy to swap out. But it's NOT what most parts store employees think of as a starter solenoid. They'll try to sell you the starter RELAY (on the fender near the battery) as the "solenoid". It's not. The actual solenoid is the small cylinder on the starter, as that diagram shows.

meppwc

Steve83.............thank you for the advice. I would like to try testing this starter myself using the meter that you are suggesting. Would you mind providing me with the steps to perform that test. This will be a first for me and I want to learn.

Thanks

greasyknuckles

pretty much put the clamp on part around the batt. cable, disconnect
the coil wire so it won't start and have someone crank it or jump
the solenoid while you watch the meter.

Steve83

First, you'll need to buy a DMM with a DC high-amp clamp. The one in that pic hasn't been made in years, so you probably won't find that exact model. There are many similar, but most will only measure AC amps through the clamp. Make sure you get one that specifically says the clamp can read DC current (Amperes/amps). Then read its instructions & search YouTube for videos of using that particular model.

But, greasyknuckles is right - clamp on, reset zero on the meter, and watch as you crank. Some meters have a "record" function that stores the high & low readings. That's one of the reasons to read your instructions first.

But START with the battery terminals.

meppwc

So I was getting ready to perform some testing on this and found 2 solenoids..........one on the passenger fenderwell and another on the starter. I would have not expected to see that. So is this truck really using 2 solenoids?

Steve83

No. The small cylinder attached to the starter is the starter solenoid. It primarily operates the fork that shoves the Bendix out into the ring gear. As a secondary function, it closes some switch contacts to change which part of the starter is energized (making it also sort-of a relay).


(phone app link)

The thing on the fender is the starter RELAY. It merely relays the low-current signal from the ignition switch as a higher-current signal to the starter (including its solenoid).


(phone app link)