This Start Problem....

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
it was a new start switch when I put it together.

I suppose it is technically one wire. But it is wrapped and covered, and taped fast into the harness.

But honestly, I don’t have the time for this. It’s just going to have to be ignored, and I’ll just jump or push start it when I need to.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I'm going to ignore the issue till I have the chance to get it to the shop. Too busy, too much hanging on this car running for the next few weeks to start digging into the wiring harness right now. I know the way I work, and the schedule I have, it's a good couple of weeks of me working hard on it to figure this out. I have confirmed that the car starts just fine by jumping the two studs, or by connecting directly from the battery, so it won't leave me stranded for more than a few minutes.

At least I know where the problem is happening, so handing it over to Ship's to do the work won't be like, "Hey, something's wrong, go find it."
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
Basically, it comes down to this. There is somewhere in the line from the ignition to the start solenoid, too much resistance. So I gave it a try during the last light this evening, to try to trace the wire back. I’m checking voltage at every junction, and using a light bulb to test that same spot while it has a load on it.

I only managed to trace it back through the first pigtail, then to what I think is the first multi plug up against the firewall. But I’ve not been able to get it to come apart to do the test.

Wire end while connected to stater ~8v
Wire end free 12.68
Wire end with light 11.80
At first pigtail free 12.68
First pigtail with light 12.02 (cleaned)
Wire end after cleaning first pigtail 11.95
 

MountainD

Technical Excellence Contributor
THAT is how you figure shit out. I have owned enough rovers to never throw parts at it anymore (well 90% of the time). You are doing it correct--find the error/part, never treat a symptom. Good work.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
Not sure what I'll do if I find anything, especially if it happens to be one of those multi plugs!

Does anyone know where the actual start relay is on the old V8 Rovers? This is a V8 harness, and it shows a relay in the wiring diagram, just don't know where it is on the truck.
 

Napalm00

Technical Excellence Contributor
you will need pliers to pull apart the multiplug if it hasn't been done in a while, repack it with dielectric grease when you reassemble after cleaning it out .if you have a starter relay it will probably be under the fusebox cover, yellow in color on the lower right side.

if you do have a relay is much less likely that the ignition switch has gone out, as they usually die due to the excess load on them without a relay. even though the switch is new, you should still test it as they are notoriously shitty
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
So I managed to get the plug at the bulkhead undone to test the wires. Not sure what is really going on there since at first I got nothing from any of the wires when turned to start.

After plugging it back in so that I could also put the probe in between and measure, I was able to see voltage. The wire that goes to the starter shows about 8 volts when it is plugged in (same as at the starter) but only about 0.02 volts when not plugged in.

So little to no voltage comes through that wire when there is no load on it at that junction, but I get a full 12.6 volts several feet further down stream (without a load).

Now I’m baffled.
E7F7EAB6-D18E-4B5B-B036-76138C7FAA3D.jpeg
 

Napalm00

Technical Excellence Contributor
Test resistance from the multiplug to spade

Provide a true 12v to the multiplug and measure voltage at the spade . Check for voltage drop

If you have excessive resistance or voltage drop you know that segment is suspect . Do the same for each section of the circuit to isolate the issue.

Or run a fresh jumper from the ignition switch to the spade and test voltage again .
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
Ah. Yes. I think I get it. How about a single line directly from the battery too that wire at that spot to see if it activates the starter correctly?

I did this at the solenoid, and noticed a big difference.

Not sure if this answers my odd findings at the plug though.
 

jymmiejamz

Founding Member
Callsign: KN4JHI
No point in measuring resistance if you are going to measure voltage drop. Resistance is a bad way to check wiring anyway.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
One way or another, I’m looking for the point where the drop or resistance is happening. But why would resistance be a bad way?
 

jymmiejamz

Founding Member
Callsign: KN4JHI
One way or another, I’m looking for the point where the drop or resistance is happening. But why would resistance be a bad way?

If you find a problem with resistance, that is great, but if a wire passes a resistance check, that doesn't mean the wire is good. The easiest way for me to describe why it is a bad test would be in a scenario where most of the strands in a wire are either broken or corroded. As long as one strand isn't broken or corroded the resistance check will pass and you won't have an open circuit when measuring resistance. A voltage drop test will very clearly indicate there is a problem.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
But I thought a small gauge wire has more resistance in a given circuit than a larger one of the same length. So wouldn’t a last strand hanging on do the same thing?

Mainly I’m looking for old, corroded connections.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I did not work on this today. The vehicle seems to be back in a good mood, and the problem is difficult to trace if it can’t be replicated when I’ve got the probes on the wires!

It has a tendency to act normal for a while, then go back to about 25-30% of the time not starting.

I cleaned all connections on the engine side of the bulkhead, so maybe that made some kind of difference? Time will tell.

I am going to revisit that plug, and make sure I was getting accurate readings from my tests. But at least it is starting normal for now.

EDIT: By the way, I actually am measuring volts, not ohms in my tests. But mainly because it is just easier, and because I am not even sure what kind of resistance there “should be” in the first place. With volts I have a place to start: whatever the battery is at it’s terminals.
 
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RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
After cleaning the pig tail connection to the starter, and the main plug on the engine side of the bulkhead, I did see a voltage increase of almost 1v, pushing the voltage at the end of the wire at about 9+ volts. For one reason or another, the truck started very well for about two weeks. That is, starts instantly every time.

But it has started acting up again.

My Rover electrical engineer friend over here (featured on the cover of this month’s Rovers magazine!) just told me that he also checked the voltage at the connection to the solenoid and found it to be only 9.6v, which is close to where I am when not having start issues.

I’m wondering what voltage others get at that spot. That is, positive test lead on the blade on the solenoid while it is connected to the ignition key wire. Ground to the engine nearby, disconnect the fuel solenoid, then turn the key and see what type of volts you get while the starter is turning.

Im going to try this again today to see if I have again lost voltage since last tested a few weeks ago.

Why do I get ZERO voltage at this plug, unless the plug is plugged in? When I measure it unplugged = 0. Measured by fitting probe into connection with it plugged in = 9+ volts.

629EF9D2-38D4-4BD9-AE70-518F433BF9B3.jpeg
 
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RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
OK, I managed to get the time to check out the voltage at the relay.

When I measure where the voltage comes to the relay, pin 30, I get 12.7 volts, but that drops to about 9 volts when I turn the key.
When I measure where the voltage comes out of the relay, pin 87, I get 0 volts, but about 9 volts when I turn the key.

I get a voltage drop of 2 volts at the battery when I turn the key.
 
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RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
I’ve tested every spot along the wire where I can get a probe into. Essentially, working from the relay forward to the start solenoid, I get a steady step down in voltage to the point where there is as little as 7 volts at the starter even while there are 12.6 at the relay. But not always. When it works as normal, I have 9.8v or so. The relays are all working. The starter acts 100% normal when jumped at the main lugs, or when I apply 12v to the solenoid. The start switch shows 12.3v or so when I turn the key and have the probe on it. But I’ve never been able to watch that spot when the fault occurs, so after attempting to do so after 20 or 30 tries, I gave up.

So... what would you do next?
 
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