Commer PB pick up

Roatavator: My workshop manual gives your chassis number designation as follows PB=PB series forward control. C=1725cc 4 cylinder petrol engine. M=Manual gearbox.

Pleased I could assist with your starting problem.

Your pictures don't show the corner of the engine with the brake master cylinder reservoir. (rear drivers side) The cold start reservoir would normally be there. Otherwise the pipework of your engine is similar but slightly different to mine.
 
Hi Colin
Thanks for your help, sorry about pics, difficult to see what you're looking at in the engine bay in bright sunlight, no better in the gloom of the garage!
As for engine, quite glad its a diesel given the fuel consumption!

Peter
 
I'd have the diesel for preference too!

Looking closer at your pics, the difference does seem to be the way the Thermostart is piped up. Yours is fed straight from the fuel filter, whereas normally the return pipework from the leakoff pipes would go to a small cast alloy pot with three outlets, in front of the brake fluid reservoir, and this would feed down to the thermostart. Frustratingly, this is the bit I can't see from your pics. This pot saves a little diesel from last time you ran the engine, and uses it to prime the thermostart. That's not to say the way yours is done isn't right, but I can't work out quite how it functions at present.

2015_0719Commer0004.JPG

Also you can see the sediment bowl which acts as a water and dirt trap. Do you have one of these?
Bottom left of this photo is the oil bath air filter, which is connected to the inlet manifold with an air duct. This air duct makes a HUGE difference to engine noise.

Just for the record, here's the other side.

2015_0719Commer0003.JPG

And yes, it is blowing a little oil out of the filler cap!
 
Looks like the pot has been there at some time as the bracket is still there. Haven't got a clue about the Perky I'm afraid.
 
Well, whatever, the old girl starts reasonably OK. There's plenty of white smoke when cranking over before she fires, so fuel supply on start up is not a problem. At the moment she only has a car battery, I'm going to replace that with a beefier one before the winter.
 
Sorry to get all technical and boring here but please bear with me. And I've been away for the weekend in the VW, so I'll apologise for that as well!

The symptoms of your cranking time and white smoke while cranking before starting are consistent with the setup you have I think.

With the reservoir pot present the Thermostart would have fuel available BEFORE cranking, so while the button is pressed even without cranking, after 15s should ignite. Then while cranking, the flame would get drawn into the engine, then as soon as fuel pressure is up (1 or 2 seconds) fuel would be injected and the engine should fire. So that's the engine running within 2 secs of cranking.

Without the pot, and with the Thermostart fed from the fuel filter (Which is what you have) it would be more like..........Thermostart would have no fuel available without fuel pressure, so while the button is pressed, it would get hot, and it's little valve would open and air would be drawn in for a few seconds before cranking, as fuel runs back towards the tank (assuming no non-return valve), then while cranking it would take a couple of seconds to get fuel pressure, then a few seconds to drive the air out of the thermostart pipe. Thermostart would not have ignited yet, so fuel would be injected into the engine from this point, and would show cold white at the exhaust. About ten seconds after fuel pressure was up, the Thermostart would ignite using fuel pumped from the filter, and the engine should start. That's about an extra ten seconds of cranking.

This all assumes everything else is equal of course, and there are no air leaks into the fuel system. But air leaks usually show up as a few seconds running fine, then engine stops and won't restart easily, which doesn't seem to be what you have. In the winter both setups might take a bit longer to fire up.

The other benefit of the reservoir pot is that it is divided in two. Half supplies the Thermostart, and half keeps the fuel filter and injection pump under a very small positive pressure while standing, so any slight leaks are fuel outwards, not air inwards.

These Thermostart devices seem to have got a poor reputation, but in fact are very effective when working properly. Millions of Massey Ferguson tractors with Perkins engines (amongst others) have these, and start well in all weathers.

I've been reading a bit more on t'interweb (sad I know), and it would seem that the connection to the fuel filter (longer cranking) was common for heavy plant, or bio fuel, and that a fuel reservoir (preheat then short cranking) was almost universal for the smaller road engines, so I've learned a bit as well.
 
Blimey, now I know a lot more about Perkins diesels!
Thanks Colin.
I think for the moment I'll just give her a beefier battery for the winter and see how things go. I'm not too fussed about cranking over a bit longer than usual, the old girl will be kept under cover which will help to keep her a bit warmer than if outside, and I probably won't use her much in very cold weather anyway. Unless my son gets carried away when he sees this post and turns up with a bunch of spares to upgrade her!

Don't know about echos, I seem to have gone deaf since I bought the PB!
Peter
 
That's great, apart from the deafness. I don't want to suggest that you start tearing it apart or anything, but understanding what's going on can make living with it that much more tolerable.

[edit]You could get all the bits from an old MF135 tractor BTW.[/edit]
 
Indeed, I'll have a word with my non-resident mechanic when I next see him, think he knows a farm contractor or two!
 
The non-resident mechanic has arrived! Firstly, apologies for the lateness, been busy with paying jobs ;)
Thanks for all the info Colin, when I read your first post And you said it was meant to have a cold start fluid reservoir I completely misunderstood and thought you meant the old style system like lorries of the era used to have that squirted ether in. It's no wonder I got completely confused! By the look of the pictures we haven't got the bottle and possibly not the sediment bowl either but since I haven't been in "dirty clothes" and near the pick up since we picked it up I haven't been able to have a good poke around and see what we have got! I will definitely do some investigation soon as to what we've got and see if I can find find the required "missing" parts through my contacts (thanks for the tip on the MF135 being a good source), not that I want to fix something that isn't broken but if we can save the starter some hard work at the same time as making it easier to fire up I see no harm in it, especially since it would normally be there anyway.

Steve: I'm pretty sure I can speak for all of the family who have driven it so far when I say a massive thanks to you and that we're over the moon with it. It's perfect for the job/s it was bought for and should give me a few opportunities to teach Snr some mechanics and give us something else to have some "father/son time" with. It was a pleasure to meet Rich and be shown around your collection, I only wish I lived closer so I could visit more often! The Capri sounds good too, disappointed I missed that one although I'd be in the car on the way now if you'd said it was a MK2 Granada 2.8 injection (sport in other words!).

Panky: Being the admin guru that you are, would you be able to merge all the useful technical chat from this thread into the one started by Dad in the "Readers' Rides" section? Doesn't matter if you can't, just thought it would be good to have all the info in one place and in a more appropriate section!

Not sure I heard the echo either, too much P.R.T (Perkins Related Tinitus) ;)

Phil
 
You must log in or register to reply here.
Back
Top