Laboured starting TDI90

cheechy

cheechy

A2OC Donor
Ok so I'm struggling a little to understand where I can go with this one.

I recently posted a few questions around alternator - I've now replaced and cleaned up the earth leads on starter. Its improved starting a little but the car doesnt burst into life in the way I'd expect. There is no sudden crack its just almost not starting then does - very sluggish.

I tested the battery this morning and it was sitting at around 12.1v before crank, then dipped below 10v at start then back up to above 13.5v once started.

Yes the battery likely isn't optimal but it should still be enough - its a battery of age under 5 years old (Varta 110 silver 85A).

I guess I could be back looking at earth drain which I assume I can check by attaching live to engine block?

Anything else contribute to this? Camshaft sensor? Dodgy glow plugs? No errors on these that I know of.
 
Last edited:
The best way to check if your existing earth connection is the problem is to create a new earth between the engine block and a chassis point. Not sure what you meant by ‘attaching a live to the engine block’ DO NOT DO THIS!
Also I assume you have checked the battery connections?
 
Sootywg said:
The best way to check if your existing earth connection is the problem is to create a new earth between the engine block and a chassis point. Not sure what you meant by ‘attaching a live to the engine block’ DO NOT DO THIS!
Also I assume you have checked the battery connections?
Click to expand...
Haha sorry worst description from me in the world :D

What I meant was measure for drain by attaching a multimeter to the block and to the body.

Likely I do need to create a new earth - any suggestions on where to take from and to?
 
cheechy said:
Haha sorry worst description from me in the world :D

What I meant was measure for drain by attaching a multimeter to the block and to the body.

Likely I do need to create a new earth - any suggestions on where to take from and to?
Click to expand...
Engine mount to drivebelt tensioner is where i routed mine when it failed on my 75. I did a thread, search "Starshine" if it helps
 
Remember to check all the connections onto the battery and the battery earth lead onto the chassis. 12.1v is pretty flat and would expect a bit more than 13.5v once running. If you leave the engine running does the voltage increase over 13.5v ? Your starter motor may be failing dragging down the battery on cranking. Does the car start better if on jump leads?

How is the fuel system? How recent is the fuel filter? Tandem pump good? Any smells or smoke when running?
 
  • Like
Reactions: nod
Doesnt go above maybe 13.5 to 13.8. I certainly used to get above 14v.

I'll try the new earth lead as a cheap win but am prepared for a new battery - the car sat a few months with light use and I suspect it may have sat too low for a period of time. Need to check for drain again.

Fuel filter replaced around 10-12k ago (I've replaced twice now - the original was in place for what looks like 120k miles and was disgusting).

How do I check the tandem pump? No error messages as such.
 
When my tandem pump went bad on the AMF it was pretty obvious - the car would run but then take several cranks before it would start, and the slick of diesel running down that side of the engine pooling on top of the subframe was pretty obvious by smell and then 'wet' fingers when feeling around the pipes and side of the engine down there - as well as the coolant pipes getting sticky.

I think I've seen recommendations from @audifan in another thread to put a piece of clear tubing onto the diesel feed and look for bubbles as evidence that air is getting pulled into the diesel pipework somewhere but I don't remember the details.

What about the alternator? A new battery may give you visible 14.something volts for a few days, but could be disguising a problem such as the battery earth connection as stated above.
 
For the tandem pump, replace the short rubber fuel pipe from the top of the metal fuel in line onto the tandem input with a similar length of tight fitting clear diesel resistant tubing. Start the engine and allow to fully warm up. Observe the clear fuel tube for small bubbles rising up into the tandem. This shows you have an air leak into the fuel system somewhere. Turn the engine off and keep checking the clear tube to see if the level of the fuel starts to drop back down the pipe, this is a worn tandem as it is no longer able to maintain full fuel.
 
Robin_Cox said:
When my tandem pump went bad on the AMF it was pretty obvious - the car would run but then take several cranks before it would start, and the slick of diesel running down that side of the engine pooling on top of the subframe was pretty obvious by smell and then 'wet' fingers when feeling around the pipes and side of the engine down there - as well as the coolant pipes getting sticky.

I think I've seen recommendations from @audifan in another thread to put a piece of clear tubing onto the diesel feed and look for bubbles as evidence that air is getting pulled into the diesel pipework somewhere but I don't remember the details.

What about the alternator? A new battery may give you visible 14.something volts for a few days, but could be disguising a problem such as the battery earth connection as stated above.
Click to expand...
Replaced last week Robin - first thing I did :(
 
So the starting has got worse after the replacement tandem? New or used?

You could have multiple issues including:

Battery, earths, powers, starter, alternator, injector loom, engine sensors, glow plugs, relays, ignition switch, air in the fuel, lack of fuel, tandem pump, air filter, ASV, partially blocked exhaust and possibly more...
 
Would it not make sense to connect your battery to a charger and get it fully charged before exploring other options? 12.1v is below any sort of acceptable for resting voltage and a 5-year old Varta should certainly do better.
 
audifan said:
So the starting has got worse after the replacement tandem? New or used?

You could have multiple issues including:

Battery, earths, powers, starter, alternator, injector loom, engine sensors, glow plugs, relays, ignition switch, air in the fuel, lack of fuel, tandem pump, air filter, ASV, partially blocked exhaust and possibly more...
Click to expand...
Sorry was replying to the question from Robin directly. I've replaced the alternator and it has improved a little but I think this is mainly due to me cleaning up earthing points. i suspect there is nowt wrong with the alternator.

I charged the battery already but its either not holding or (most likely) thinking about it I likely have a drain somewhere.

The only things I think could be doing it would be the Pure DAB unit, autolight unit and dashcam. I'll disconnect all and measure.
 
Sorry Mr stupid here. Mrs cheechy took the car for a 70 mile round trip earlier today...low and behold the car is holding a charge and reporting 14.1 to 14.2v in operation and car start very solid. Likely the battery ran lower when I had originally changed the alternator and didn't give the battery a big charge.

I still think I've got a drain issue so will try and narrow this down but now at least I think the battery looks ok and the alternator change call looks to have been a good one.

Thanks all
 
cheechy said:
Likely the battery ran lower when I had originally changed the alternator and didn't give the battery a big charge.
Click to expand...

I'm left wondering what sort of charger you used, and how you decided that the battery had been given an effective charge?
 
Charger was not the issue... It was timing. I had charged a day or so before i changed the alternator and after a couple of trips the battery did run down a bit. It was as if the alternator was not completely gone but not enough to charge the battery properly
 
Is the idle speed stable, and what values do you get at start up and 3min after staring the car? Really sounds like, something to do with the fuel delivery, as mentioned above as well, I would definitely start by changing the fuel filter, especially if it hasn't been changed for many years. Then compression test to see if one or more valves might be sticky.
 
Sylvester said:
Is the idle speed stable, and what values do you get at start up and 3min after staring the car? Really sounds like, something to do with the fuel delivery, as mentioned above as well, I would definitely start by changing the fuel filter, especially if it hasn't been changed for many years. Then compression test to see if one or more valves might be sticky.
Click to expand...
Yup idle good. As above the alternator replacement did appear to have resolved.
 
You must log in or register to reply here.
Back
Top