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RRC cutting out w/electrical draw... suggestions please

sillysod

sillysod

In Fourth Gear
I have found a strange problem with my RRC that has been driving me nuts. When driving down the road the vehicle would start to "cut out". It feels like:

A) Spark is being cut for a millisecond or so
or
B) Fuel pump is being cut out for a millisecond or so

I have had this problem for months but only a week or so ago I that if you introduce an significant electrical draw the problem will appear. I never realized before that it was always happening when it was either dark out or the heated seats, stereo etc was on.

It is quite noticable when you use the window switches and try to close an already closed window, and if you flick the fan blower switch back and fourth quickly it becomes noticable as well.

Otherwise it feels like a miss (albeit a serious miss) when an electrical draw is introduced it misses so badly it almost starts to buck.

Based on suggestions from other RR enthusiasts I changed the TPS and replaced the ground cables from the batt to the body and engine.

The truck still cuts in and out when there is a high amount of electrical draw on the system AND the vehicle is going over 100 km/h.

The fewer the electrical devices turned on (and therefore the less draw) the faster the vehicle can go until it acts up.

ie. seats, stereo, lights, fog lights all on at 110km/h = problems
lights only on = no problems until 125km/h

IT IS NOT A PROBLEM WITH LIGHTS ETC. these are only examples. Any electrical draw (putting a window up or down) can cause this to happen.

It does not matter if it is in 4th gear or 3rd gear, engine rpm does not affect this, nor does gentle acceleration or de-celeration. It is extremely strange!

I have spent a lot of time fixing everything on this truck to make it like new to the point where I can park it and it actually retains all fluids. :eek:

Truck runs perfect except for this one thing and I have to figure out how to sort it out!!!! Please give some input as I do not want to start just throwing parts and $$ at it.

Help is much appreciated!
- SS

http://cgi.ebay.ca/ws/eBayISAPI.dll...MEWN:IT&viewitem=&item=320082512568&rd=1&rd=1
 
Check the WIRING from under the seat to the fuel pump. You probably have rotten wiring. I bet if you take up the rear carpet and access the plug to the fuel pump, you are going to find with your voltmeter that you are not getting 12+v to the pump itself, irrespective of the load from lights and such, and when the additional load comes in, the voltage drops even further. Check it out and see.
 
What I did on mine with the same problem was to run a pair of new wires under the carpets to the rear cigar lighter circuit, and she has been running fine ever since.
I was not sure if the rest of the circuit(fuel pump relay, etc) was also faulty, and I knew I was getting a solid 12v at the cigar lighter when the ignition was on, so I went with that, and two thousand miles later, she is doing fine. Except for yesterday, when I blew the fuse on the cigar lighter circuit(not related to the fuel pump, I dropped a penny into the lighter by accident) and I cannot find the fuse!
But, certainly, your problem is the fuel pump not getting enough voltage, for one reason or anotehr. If your lights are strong, and your battery is getting charged, it's probably not your new alternator.
 
Okay this weekend if i will take a look at it. I have no rust on my RRC (even the frame still has the factory paint on it) so I can't see how the wiring rotted out - however it is possible that it dried out and is cracking off....
 
sillysod said:
Okay this weekend if i will take a look at it. I have no rust on my RRC (even the frame still has the factory paint on it) so I can't see how the wiring rotted out - however it is possible that it dried out and is cracking off....
Click to expand...
It's worth looking into. Pull the plug at the fuel pump and see how much voltage you are getting there. It's a free thing, no money, not cutting needed to find out.
 
Aswell as the earth cables, take a look at the positive side of the supply circuit.
IIRC the battery pos cable has a terminal block mounted to the inside face of the right hand chassis rail just behind the battery somewhere. Then pos heads from there to the starter, and from there it supplies most other circuits.

Try measuring battery voltage, engine running at a high idle, whilst someone operates various electrical loads. If voltage drops then you have a charging/battery problem, or a high resistance connection somewhere.
Try the same tests but use battery pos post and chassis. If voltage is lower the you need to look at your earth straps again.
Do the same tests again but measure pos at the starter pos connection and neg at the battery. This time, if it's higher than the first test, it's a fault between pos post and starter.
Try measuring running voltage at the fuel pump, and at the ignition supply, and ECU supply while loading the electrics up..
The trickiest high resistance faults are usually the ones that only become apparent under load. They test perfectly fine using a multimeter as there is no current flowing when testing, and it's impossible to use a multimeter to check resistance when the circuit is live.
What you can do is measure voltage across connections while they're under load. If there's more than the tiniest amount of voltage drop across a connection, then there must be resistance.

If ever you want some serious in depth fault-finding time (I spent 10 years in the Army fixing electical/electronic faults on far bigger and nastier bits of kit than RR's!) maybe we could meet up some time. A few guys from Edmonton, and us bunch in Medicine Hat are planning for May long weekend in Cypress Hills if you're up for it.......bring your wiring diagrams!

swag
 
swag298 said:
Aswell as the earth cables, take a look at the positive side of the supply circuit.
IIRC the battery pos cable has a terminal block mounted to the inside face of the right hand chassis rail just behind the battery somewhere. Then pos heads from there to the starter, and from there it supplies most other circuits.

Try measuring battery voltage, engine running at a high idle, whilst someone operates various electrical loads. If voltage drops then you have a charging/battery problem, or a high resistance connection somewhere.
Try the same tests but use battery pos post and chassis. If voltage is lower the you need to look at your earth straps again.
Do the same tests again but measure pos at the starter pos connection and neg at the battery. This time, if it's higher than the first test, it's a fault between pos post and starter.
Try measuring running voltage at the fuel pump, and at the ignition supply, and ECU supply while loading the electrics up..
The trickiest high resistance faults are usually the ones that only become apparent under load. They test perfectly fine using a multimeter as there is no current flowing when testing, and it's impossible to use a multimeter to check resistance when the circuit is live.
What you can do is measure voltage across connections while they're under load. If there's more than the tiniest amount of voltage drop across a connection, then there must be resistance.

If ever you want some serious in depth fault-finding time (I spent 10 years in the Army fixing electical/electronic faults on far bigger and nastier bits of kit than RR's!) maybe we could meet up some time. A few guys from Edmonton, and us bunch in Medicine Hat are planning for May long weekend in Cypress Hills if you're up for it.......bring your wiring diagrams!

swag
Click to expand...


Thanx swag. I am sure I will get it sorted out. This truck rarely sees highway speeds so the problem is not huge, but I would like to get it fixed. It is the only thing left on this truck that is not working properly.

I have a new MAF on the way as Land Rover Calgary seems to think that sounds like the problem. I will check the voltages and switch my alternator this w.end and see how I make out.

Worst case scenario i will drive it down to med hat and hire SSC (Swag Service Company) to take a look at it. I am sure it will be better than getting the guys at Land Rover Calgary to look at it.
 
swag298 said:
A few guys from Edmonton, and us bunch in Medicine Hat are planning for May long weekend in Cypress Hills if you're up for it.......bring your wiring diagrams!

swag
Click to expand...

I couldn't risk getting the wheels on the wife's RRC dirty. ;)
Might be out with a jeep though...
 
speed sensor?
that will throw a paddy if it isnt right

also- check your main wiring loom connector block- drivers side in the engine for crud- a build up of crap will make the resistance of the connector block build up with heat and it might not be getting any signal when other stuff is being switched on
 
Hi, try changing the spade fuses and checking all have good connections,i have seen fuses do this(ex road side patrol/mechanic) and they look good and are not blown but furing on the blade ends can happen and will give some very funny problems,also blade fuses are cheap and if it works it's a quick fix,let us know how you get on,cheers.
 
Grumbleweed said:
speed sensor?
that will throw a paddy if it isnt right

also- check your main wiring loom connector block- drivers side in the engine for crud- a build up of crap will make the resistance of the connector block build up with heat and it might not be getting any signal when other stuff is being switched on
Click to expand...

The truck is pretty much spotless, it was completely stripped for paint last year and since has only seen a little slush and snow. Under the hood it is clean but it doesn't hurt to check.

I am assuming since you drive on the wrong side of the road it will be on my pass side?
 
hi just wondered if the engine management light comes on//this looks like a fork and is this a p38 2.5 bmw engine????? if so i maybe able 2 help
 
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