Hi everyone, my first post here , I have a 1987 JCB 1400b that's been slowly giving me cranking issues since the weather's been getting colder. I just installed a new starter because the large terminal on starter corroded and broke off.the battery is new also I still have to jump start with my truck to get it to crank a little better but not that good like it should. Now today I jumped it with the screwdriver at starter and it cranked like unbelievably fast? What and how should I test for to see were the voltage is lost,any ideas would be appreciated!
Did the new started come with a new solenoid?
If it cranks slow every time, just take a multimeter and work your way from the positive battery post back to the negative post, looking for low voltage drop across every connection and cable except the starter. Or any number of other ways to go about it. You could start with one lead on the starter terminal and the other on the negative battery terminal, thinking that you'll be able to tell if the voltage drop is in the positive cables, or in the ground cables, sort of test it in the middle to eliminate the biggest chunk you can. The way you describe the solenoid is the obvious suspect, but were you leaning on the ground cable at the same time???
Starter and solenoid are brand new and I touched screwdriver in between small start terminal and large positive terminal,thanks for your response.
Yes ,starter came with new solenoid
I also replaced the neg battery wire with 01 gauge but not pos ,didn't look bad but maybe I should.is that tru it could loose its voltage carrying capacity over time?
Did you use a replacement battery of the correct size and amps. Like Delmar have said if your ground and hot is good, I would first use my jumper cables and double off the neg battery post to the engine at two different spots and recheck. It kind of sounds like the voltage from the key switch does not have enough volts all the time to make the starter want to engage, run a fused wire from the battery plus and touch the key switch wire lug. If it cranks good then trace back your connections to the key switch, may be a neutral switch, key switch, or a relay that's causing your issue.
Of course, usually it's the connections that rot out, but the acid can travel up the wires and rot out the copper wires at the center of a cable sometimes to. That's where the multimeter comes in handy, if you have the battery shows 11 volts cranking but the starter terminal only shows 8 volts to the negative battery terminal then you're losing 3 volts between the pos terminal and starter terminal. That 3 volts will show up as heat eventually, so you may find the connection by feeling for the warm one after enough cranking. Like sheepfoot said, you can bypass the key to see if that is affecting the cranking speed somehow.
OK I put volt meter on starter pos term to pos bat showing 12.4v even while cranking so was looking inside were ignition switch is and when cranking volts went down to 8v.now while it was cranking I heard a funny buzzing/clicking from what I found out is the relay with two heavier wires and two smaller wires. One of the heavier wires went to key switch and other thick wire went to starter, so what I did was jump the two heavier terminals together on relay and cranked like it should!. I took the housing off relay and sanded the points clean then tried again to crank without jumping relay but didn't make a difference. But as long as I jump relay cranks perfect
hi sounds if it is the start inhibit relay as you have by passed the relay and it starts as should by joining large wires you need to look at the feed/switch wire and earthside of the relay do continuity of the earth side if no good run new or trace back the power side will run possibly through forward reverse and dump circuit for drive so need to trace that wire into loom as this relay stops you from starting in gear on your forward reverse side.
How would you test the relay itself to see if it's bad
Test the relay by checking the voltage across the smaller two wires while cranking. DVM should read about 10 to12 volts. If lower, the relay may not be fully energizing. Jumper it directly from the battery (disconnect the two smaller wires first), and see if the cranking speed is normal. If normal, relay is ok, and the problem is low voltage to the relay. Next, while cranking, check the voltage drop across the load contacts (the larger two wires). It should be no more than 0.1 to 0.2 volts. If this test fails, the relay is bad (burned contacts).
I bench tested the relay,put 12v to small terminals and contacts closed then I tested large contacts with ohm meter and read between .01and .03 ,so the relay should be good right, then why when I touch two larger terminals with screw driver it cranks good .like HORSEPULLER said to put jumper wire from pos bat to small terminal on relay but which small terminal do I jump with pos jumper, one is solid black (which I presume is neg)and other is green and red striped which should show 12v correct
When you go to start the switching part of the relay or the smaller two wire one will be earth and should be ground and the other is the switching side controlled by start inhibit part does that wire have 12 volts or very close to that when crankinig if not you need to follow that back to find voltage drop
johncabernet1 - Your bench test low ohm reading does seem to say that the relay is OK, but... That sort of test is a no-load test; the relay contacts are only carrying a tiny current and almost no power. The best tests, in general, are loaded tests. Your screwdriver-across-the-contacts check puts an additional low resistance path in parallel with the relay contacts. Having this test speed up the engine cranking RPM indicates that the relay contacts are not providing the low resistance path that they should. The jumpered loaded test I suggested in my previous post is the final test necessary to condemn the relay as bad under load, if it is getting a full 12 volts of actuation voltage. Actually, jcb jeff's post suggests a better, easier test than my jumpered method. Without disconnecting any wires, using your DVM on a DC voltage range able to read 12 VDC, jumper the meter negative to the battery negative and probe the two smaller relay terminals while cranking. One will read almost nothing, 0.05 volts?, the other should read about 12 VDC, indicating that almost all the voltage in the circuit is being dropped across the relay coils. If you get about 12 volts, the relay is getting full voltage and is bad. If you get a low reading, it indicates resistance and a voltage drop elsewhere in the circuit, which is preventing the relay contacts from closing properly, and which you can find by probing back through the circuit, looking for a voltage drop.
Sounds like the relay is getting weak, try "swapping" the relay with another or buy a new relay, their not that expensive and it's always good to have a spare on hand.
OK thanks horsepuller I'll try that test later today
OK I hooked up volt meter ,jumping neg bat to meter and other end of meter line to take readings from both small terminals,solid black small terminal read between 4+6v while cranking ,other small terminal red and greyen read between 6+8 v while cranking and that's with both small terminals still coneccted ,so dores that sound like I'm loosing volts in between? On the small black side of relay the jumper alligator clip accidentally touched steering column metal while I was cranking to check meter and at that time engine cranked real good? Is that possibly a bad ground to relay
Hi It sounds like you have accidental found you fault check continuity of the earth side of the relay but you will need to disconnect the wire from the relay first if all else flails you could run a new earth but be careful that you dont do away with the neutral start side of the relay system or some one could be injured if the machine starts in gear.HAPPY PROBBING
I agree with jcb jeff that it looks like the starter relay has a bad ground. If you decide to add a parallel ground (which looks like it would keep intact the cranking safety features according to my wiring diagram) please check the following to make sure. Cranking should be disabled by any one of the following: forward or reverse direction selected, or foot or loader dump switches selected. Good luck with your repair.
Thanks for everybody's help.horsepuller you have a wiring diagram you could post so I could see it ,I have a parts book for my model but it doesn't show wiring diagrams. /1987 JCB 1400 B /