Rev counter issue and cold start

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jockodipunto
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Rev counter issue and cold start

Post by jockodipunto » Mon Mar 11, 2019 10:29 pm

Good evening all,

I am after a little advice.

My rev counter had decided that it no longer wants to behave. From cold start it doesn't want to work at all. After a few miles of driving, the rev counter begins to flick all over the place and is then accompanied by a flashing 'hold' light. As I drive on, and the engine begins to warm, the rev counter gradually begins to zero in on the correct revs and begins to steady, at which point the 'hold' light goes off and the rev counter then behaves normally. I am assuming that this is a faulty NE sensor (I have R reg 2.5 turbo diesel) but before I get stuck in and clean / replace, is there anything else I should be checking?


The reason I need to get the rev counter sorted is that I also have cold start problems i.e. it starts immediately after glow plug light goes out, idles smoothly for a few seconds, sounds like revs drop slightly and then it starts to shudder, misfires and shoots white smoke out the back (glowplugs maybe).

Any pointers would be really helpful. By the way, I am finding Bongo repairs quite addictive.......

Many thanks

Mark
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Bob
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Re: Rev counter issue and cold start

Post by Bob » Tue Mar 12, 2019 10:26 am

I suspect there's more, and I'm no great techie, but I've known a fluctuating rev counter be a sign the alternator is about to depart this earth.

Hopefully someone will have more thoughts. 8)
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jockodipunto
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Re: Rev counter issue and cold start

Post by jockodipunto » Tue Mar 12, 2019 8:38 pm

UUuuuugh - never even considered alternator. Any thoughts on how I can check this or do I need to wait until failure?? :(
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Re: Rev counter issue and cold start

Post by g8dhe » Tue Mar 12, 2019 10:26 pm

Start by looking at the Charge lamp on the dashboard, if it stays lit or glowing after the engine is running that tells you its failed. Otherwise check the voltage on the starter battery before starting, aprrox 12.6 volts, then when the engine is running but only idling around 13 volts and then when the revs are around 2000 rpm it should be 14-14.4 volts, if its not in that range then the alternator is suspect.
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Re: Rev counter issue and cold start

Post by Northern Bongolow » Wed Mar 13, 2019 12:56 am

As above by the boys, alternator diodes waving bye bye. The revs dropping after initial start could be the white plugged solenoid on the driverside of the engine next to the rocker cover given up, or the pipework to it broken, you can swap the plugs over whilst cold to test this, search cold and start and solenoids in the search tab.
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Re: Rev counter issue and cold start

Post by jockodipunto » Wed Mar 13, 2019 9:06 pm

Thanks all. I will be getting the voltmeter out this weekend to check the glow plugs so will drop it across the battery and test incoming voltage etc.

Cheers all.
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Re: Rev counter issue and cold start

Post by jockodipunto » Wed Mar 13, 2019 10:19 pm

Hello all - just nipped out to check the alternator and this is what I found -

Before starting - 12.95v
Idle - 14.56v
2000 rpm (+/- 20rpm, my 8yr old volunteer had to stretch to reach the accelerator pedal :) ) - 14.58v

Does that mean I am outside of the recommended charge rate? Over charging maybe?

I kinda get the feeling (there is no evidence to support this) that the rev counter needle seems to be heat sensitive. Once the engine has warmed slightly the rev counter reads correctly and from a warm start the rev counter behaves as it should....
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Re: Rev counter issue and cold start

Post by g8dhe » Wed Mar 13, 2019 11:46 pm

Well if the voltmeter is reading correctly its just about OK, but 14.6 volts is right on the upper limit, its where a lead acid battery starts gassing! However the intermittent rev counter is not usually a problem with over voltage, normally it has problems when the battery is at the other extreme i.e. reading less than 11 volts!
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Re: Rev counter issue and cold start

Post by jockodipunto » Thu Mar 14, 2019 12:58 am

I will double check and recalibrate the voltmeter as the engine off battery volts looks a little on the high side (or see if I can borrow a different volt meter just to double check) based on what I have read elsewhere on the forums.

I also now recall that when we had the SB battery replaced for a Bongo recommended one (Bosch S4 S4 Battery 335), after the BONGO failed to start, the RAC chap mentioned the alternator output seemed good.

Okay - I will continue the investigations, and once again thanks for all the help!
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Re: Rev counter issue and cold start

Post by teenmal » Fri Mar 15, 2019 12:49 pm

jockodipunto wrote:
Thu Mar 14, 2019 12:58 am
I will double check and recalibrate the voltmeter as the engine off battery volts looks a little on the high side (or see if I can borrow a different volt meter just to double check) based on what I have read elsewhere on the forums.

I also now recall that when we had the SB battery replaced for a Bongo recommended one (Bosch S4 S4 Battery 335), after the BONGO failed to start, the RAC chap mentioned the alternator output seemed good.

Okay - I will continue the investigations, and once again thanks for all the help!

I would definatley retest with a known working /accurate meter.Also worth while checking the wiring/connector to the NE sensor.

Take care.
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Re: Rev counter issue and cold start

Post by jockodipunto » Fri Mar 15, 2019 10:53 pm

Quick update - I borrowed a friends multi-meter and mine appears to be reading 0.4 - 0.5 volts high so that has gone back via Amazon Prime God bless em.

Just one other quick question before I get back into the engine tomorrow morning, is there a reliable way to test the glow plugs without removing them?
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Re: Rev counter issue and cold start

Post by jockodipunto » Fri Mar 15, 2019 11:13 pm

Sorry all - just had one other thought. If my NE sensor is misbehaving, could that be sending odd signals to the ECU that controls the glow plug relay which perhaps might be shutting them off early - hence white smoke when cold????? I can't help but think that the rev counter and lumpy running when cold might all be somehow related?
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Re: Rev counter issue and cold start

Post by jockodipunto » Sat Mar 16, 2019 4:16 pm

Quick update (and getting out of the wind for a cuppa)

I j.j.j.j.j.jiggled the NE sensor and the rev counter flicked all over the place. If I push the wires gently against the body of the sensor then the revs just die entirely. I did remove the unit and cleaned it all up but this made no difference so will order a new unit. Are they available via the shop? 2.5 turbo diesel.

Next job - cold start solenoid but might need to do this first thing in the morning.

Van is currently idling away over some cardboard hoping I can locate oil drop and diesel drip - happy days.
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Re: Rev counter issue and cold start

Post by jockodipunto » Sat Mar 16, 2019 9:43 pm

Right, a bit more of an update (amazing what can be achieved when ones spouse alters ones priorities), anyhoo there is approx. 11.4volts to the glow plug bar which then drops to zero once the glow plug relay clicks. Not tested the glow plugs as yet as I couldn't quite get to them as the cold start relay bracket was in the way and there was an odd bolt holding it on (not got a spanner for it). I will whip off the engine bridge tomorrow so I can get to them better OR get a socket set that fits the bolt - :P

I believe the van was still a touch warm from my shenanigans earlier so the cold start black relay (left one) hadn't activated but neither had the white socketed one - AH HAH!. I swapped the white plug on to the other solenoid and this activated the relay and revs bumped up - looks like the right hand (white plugged one) might be duff so will replace.

Also, while degreasing under the engine, my coat sleeve caught under the oil filter, turns out the filter is weeping oil - might have found the leak...

AND - while fiddling with the NE sensor earlier I must have caught my other sleeve on something as it really smelt of diesel - maybe I need to change those nightmare diesel seals - is that really as bad as people say on the forums?????

Anyway that is it for the night. Time to look for some cold start solenoids. Should I change them in pairs.

Cheers all and thanks for all the advice.

Mark
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Re: Rev counter issue and cold start

Post by fatcatlawyer » Sat Mar 16, 2019 10:19 pm

The matters that you raise are exactly the situation I have with my bongo. It has been like that for at least 4 years with no sign of getting worse.
My mechanic suggested that the sensor had given up the ghost, until I told him that after 5 mins it worked fine, so that rules out the sensor so he thought it could be the seating of the sensor or the contacts, but I have not got round to checking this I have just put this foible down to a "quirk"
Ian G
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