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Low Amps When Trying to Start

drcomanche

NAXJA Forum User
Location
Lusby, MD
So, I have replaced the Starter, Battery, and Cables a few times each since people keep telling me that's the problem, but it never fixes it.

Basically, whenever I turn the key to the start position, it gets such low amps that the starter can't crank over the flywheel. It trys, but fails to get even one rotation out of it. I had the starting system tested, and it said I was working with something like 30 amps on start from an 800cca battery. I have cleaned every contact known to man on the engine and body, including the big 3.

Whenever I cross the starter posts with a wrench, I can get it to turn just fine, like nothing was wrong with it. It also starts perfectly when attached to another car via jumper cables. Originally, it only had this problem after driving for a while, and even then, it didn't happen often. Then it gradually progressed to the point where it happened only when the truck was hot or had been run. Let it sit for ten, and it would start fine. Now, it won't start at all. I have to put my key in the run postition and start it by arcing the starter.

Anybody have any ideas? It's been like this for months now, and I can't get anywhere with it. Any help would be appreciated.

It has an I6 engine with an AX15
 
what year?

if renix, have you bypassed the goofy starter relay with a regular 4 pin jobby?

What's your ignition switch look like?

Have you replaced the head to firewall braided strap?
 
1988 Comanche with a 1993 homebrew swap with a Cherokee. I didn't do the swap, so I don't know what stayed and what went.

Ignition switch is the old style on a tilt column. Haven't had a chance to look at it, since it's a pita to get to. Firewall braid strap was not replaced, but both ends were removed, cleaned, and sanded for ample contact.
 
try replacing the firewall strap. It can look good, but since it's that wocven strap corrosion kills it.

If you can get a picture of the area in front of the relays that will help.

We can see if it's renix wiring or if they transferred all of the HO stuff.
 
What would look different about it? I have a fairly good idea what it looks like since I've been seeing it for the last 2 months. I know it is a 2 plug connector to the relay box, if that's any help.

Do you know where to find any other ground straps? I have tried a couple of sites but I can't find anything. Is there another type of wire I can use for a replacement?
 
So, I have replaced the Starter, Battery, and Cables a few times each since people keep telling me that's the problem, but it never fixes it.

Basically, whenever I turn the key to the start position, it gets such low amps that the starter can't crank over the flywheel. It trys, but fails to get even one rotation out of it. I had the starting system tested, and it said I was working with something like 30 amps on start from an 800cca battery. I have cleaned every contact known to man on the engine and body, including the big 3.

Whenever I cross the starter posts with a wrench, I can get it to turn just fine, like nothing was wrong with it. It also starts perfectly when attached to another car via jumper cables. Originally, it only had this problem after driving for a while, and even then, it didn't happen often. Then it gradually progressed to the point where it happened only when the truck was hot or had been run. Let it sit for ten, and it would start fine. Now, it won't start at all. I have to put my key in the run postition and start it by arcing the starter.

Anybody have any ideas? It's been like this for months now, and I can't get anywhere with it. Any help would be appreciated.

It has an I6 engine with an AX15

1) Check voltage when cranking - look for my writeup on testing primary electrical (should be on OEM tech.)

2) Your starter will actually draw 160-190A when cranking, not 30. (!) The solenoid is good for 3-5A, as I recall, and nearly any relay will work (I got tired of replacing OEM RENIX start motor relays and wired in a DIN instead. Easier to find.)

3) There are a number of "slow crank" causes - check and cross off of your list (NB: Just because a part is "new" doesn't mean it's any damned good. Amazing how many new parts I've had to replace over the years...)

- Internal corrosion or other defect in the mains cable (power or ground - check both!)
- Contaminated connection at cable terminus (either end. Could be corrosion, could be grease/oil.)
- Burned or deformed contacts in the starter motor solenoid (it's the switch for current to the motor proper)
- Faulty connection from starter motor solenoid to starter motor (that short little cable from the solenoid into the motor casing)
- Faulty or worn commutator or brushes in the starter motor proper.

Unpowered, a mains cable should show probably 1 ohm/foot of internal resistance. Each connection can also be tested - put one meter probe on the ring lug, the other on the stud. Should read <1ohm as well - if it's more, clean/service PRN.

Solenoid contacts usually require outright replacement of the solenoid. Brushes can be replaced individually or as part of the starter motor, emery or crocus cloth may be used to clean the commutator on the starter motor armature (rinse with electrical contact cleaner afterwards, so you don't contaminate the brushes with grit and accelerate wear.)
 
The starter has been replaced multiple times with the same problems, so that gets rid of a fair amount of those suggestions. Battery cables are brand new thicker gauge cables, so direct to starter power should be just fine.

I purchased a new relay, and now it won't even do it's half crank. It makes no noise or attempt to start, whereas, with the old relay, it at least tries. The two relays have all the same pegs in the same locations, could there be a difference internally?(I haven't had a chance to pull the new one apart and compare)
 
Is the relay a little 1" cube, not including terminals? There are three versions of those relays - but the most common is the SPDT "Changeover" relay - the relay that powers two circuits at the same time usually has to be special-ordered, the four-pole "ON-OFF" relay is merely uncommon.

The regular SPDT will replace the SPST relay readily (the four-pole "ON-OFF" is SPST,) but the two types of five-pole relay won't necessarily swap.

The internal wiring diagram should be moulded into the side of the relay case, and they can be readily compared that way.

Meantime, check the internal wire resistance and the resistance of each connection, as I mentioned. May be illustrative...
 
What would look different about it?

Does it have fusible links or a PDC box?

Do you know where to find any other ground straps? I have tried a couple of sites but I can't find anything. Is there another type of wire I can use for a replacement?
Last one I did I just used a 12" premade battery cable from the parts store.
...
 
Did you ever find a resolution to this? Mine has been doing the same thing for about a year now. If I shut it off when its hot, its hit or miss if it'll start again. The starter will just stall out trying to spin the motor, only when hot though.
 
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