Mk7 Slow starting issues

[Nabla]

Hi all,

I have a 2.2 2007 SWB FWD transit (100k miles on clock), which has trouble starting up. Once it does get going it runs fine.

I thought it was the battery, since it kind of seems to be getting worse on colder days, but actually it has still been quite warm here in the UK the last few weeks, and still seems to be getting worse, or at least not improving. I have a leisure battery and starter battery both under the drivers seat, with a split charge system (voltage sensitive relay) and fusebox (feeding lights, diesel heater etc) sitting on top on a wooden panel, which I installed myself a few years ago when I bought the van - never had any issues with it.

I disconnected the whole leisure battery system and monitored my start battery for over a week or so, in fairly cold weather:

- Measured voltage was about 12.6 V - seemed healthy.
- Took the battery out and charged it in my house with a mains battery charger. Voltage after full charge was 13.39V.
- With no load, 2 days later, the voltage was 12.68V
- 4 days later 12.63V
- All seems fine so far.
- Gave another full charge on the mains charger, and connected back in van (no leisure battery circuit connected).
- After some short sparking when connecting, initial voltage was 12.55V
- 1 day later, 12.46V
- 3 days later, 12.4 V
- 5 days later, 12.35V
- conclusion is that battery seems to have healthy voltage, seems to charge ok, seems to hold its charge ok, and there does not seem to be any excessive current draw in the van draining the battery.
- Started up van with battery connected after 5 days (12.35V) and has a very slow start before eventually turning over.

I did already put a new starter motor in myself about 2 years ago, and don't drive it regularly, and mostly longer journeys (used as a camper on weekends only pretty much), so that should be ok I would guess.

I wondered if there is some high resistance between the starter battery and starter motor causing large voltage drop, so I did a voltage drop test with my Fluke 87 meter on peak min/max function, and measured 7.8V drop on one go, and 6.9V drop on another go between the battery positive terminal and starter motor positive terminal! This seems way excessive to me, but apparently this has a resolution of 250us, so may just be capturing some very fast transient (would like to get a scope on there if I had one). What should a healthy voltage drop be? I would guess only 100-200mV?

The wiring in the manual only shows Fuse 1 and a couple of connectors int battery fusebox between battery +ve terminal and starter motor +ve terminal, and between the switched input is shows starter relay, R4, passenger fusebox F77, and charger relay R1, but all fuses seem fine.

I might try disconnecting the terminals of the starter motor and cleaning with a wire brush, maybe putting a spring washer in there. I do have a small oil leak in the engine, which seems to drip down onto where the starter motor connections sit, so maybe I could try covering it after cleaning with some electrical tape.

Anyone had these issues before? Anything else I can try?

Don't want to buy a new battery only to find out that is not the issue.


Thanks

[ropecharrmer]

If you leave a healthy battery sitting in the van and it's down to 12.35V after a few days, and you're sure there's no latent current draw, that doesn't sound like a healthy battery. I'd wouldn't want to be relying on a battery at 12.35V. Your voltage drop also sounds a lot to me, but I couldn't claim to be an expert on what the right number is (though I have spent many hours working on the starting system of my Mk7).

If you want to be cautious on getting a new battery, I'm sure there are places you can go to get your battery tested before buying another.

Always worth cleaning up and checking your battery connections.

[ray1965]

i too am having similar issues tbh, i have a charging guage in the cab, that appears to show that the van charges at a variable rate depending on demand, ive had several mk6 vans and this is the first mk7, but no battery seems to last over 18 months regardless of 6 or 7

so the van starting to be sluggish to turn, i put it into a garage to be tested, both battery and charging circuit, the battery came back at only 49% of its life left, asseseed on a very expensive bit of snap-on kit, and the reason for it struggling, voltage wise it sits around 12.6 when used daily every day

now left 12 hours its only just turning over, but reads 12.6 volts idle,so i bought myself a snap batteryon tester, and yes the battery is knackered

so all this time ive been using yuasa and Bosch silver S5 batteries that are expensive, 800cca 85 ah, and the latest failure isnt even 18 months old, and they only change them one under warranty, before they blame the vehicle

so this morning ive had a read up, and i think that if ive read correctly, silver batteries are no good in a transit, it says they need a constant charging source on 14.4 to 14.8 volts in use, and without this they fail fairly quickly, my mk7 ony goes to that for short periods then drops down, and only rises on demand

so it appears i need a conventional battery rather than an expensive one, but not many manufacturers do a high cca one

the article stated that you should not fit anything other than the type fitted at manufacture, so im about to buy a std conventional lead acid battery, and the only 800cca one i can find, to see if that lasts any better

if you have stop start, then you need a different battery type again, its a minefield, then dont forget, if you change the battery for even a higher amperage one of the same type, you have to tell the van using forscan, i found that when i first put this battery on, it definately changed the way it started

[ropecharrmer]

That sounds right. I've learnt the hard way that the Mk7 can be surprisingly sensitive to the choice of battery (which seemed to be part of the issues I had with my PCM: https://fordtransit.org/forum/viewtopic.php?f=5&t=219192).

Tell you what though, when I bought the van years ago (used) it did come with a Ford-branded silver calcium battery in it which was a good battery as long as it lasted.