Help with running issues 1.9 TD aaz engine in new T25 Purchase

[Blix99]

Hello. (Apologies- I posted in the wrong area. Moderation moved - thanks : )

I wonder if anyone has any advice or experience with the 1.9 AAZ, although I think it's more to do with the Bosch VE injection pump.

I bought this T25 Doka a couple of months ago on the pretence that it had been running well and regularly for 8 years or so with this engine conversion but was then sat up during covid and wouldn't start since.

I've had it running now, but it only really ticks over - won't accelerate.

Unfortunately, unbeknownst to me when I bought it, the van had been plundered of it's best parts, so I'm not confident this engine, as bought, is in the same state as when 'running fine'

To begin with, the cold start cable was disconnected. It looks like it's never been connected with this engine. I was told the cold start was automatic, hence no need for the cable, but it definitely isn't, so I've reconnected that.

However, the engine would only really run with full cold start and, even when hot, would stall if the cold start was pushed back in. This suggested that the timing of the IP was wrong, so I've reset that and seems better now. I also changed the shaft seal.

The fuel line from the filter was disconnected at the filter, apparently to test the non-starting with a gravity fed diesel supply. I reconnected it, but the pump didn't seem to have strength to draw fuel from the filter. The filter is new.

So, I supplied fuel via gravity too, and got it idling pretty well, but it won't accelerate. It picks up momentarily, then splutters and won't even return to idle; it just stalls. Wait 10 seconds or so, and it starts again. This suggests fuel shortage to me and / or air in the system, which is why I changed the shaft seal. I have an early 1980s VW Lt28 with a 2.4D engine and similar VE pump, so am pretty familiar with the basics.

After having it run on gravity for a while, I reconnected the main fuel supply, and it idles the same as via gravity. The fuel did start moving up the clear pipe from filter to pump, but has stopped with a bubble in it and doesn't change. But, it also doesn't draw back either. I'm confused by this? No matter what I do, the bubble won't go, even if I draw through the system from the IP outlet. As soon as I reconnect the outlet, the bubble creeps back.
But it will still idle pretty well for as long as I leave it.

Could it have an airlock? I've cracked the injector nuts when idling and the revs drop with each and diesel spurts out.

Is it drawing air in somewhere? But, if this is the case, why doesn't the bubble in the supply line draw back?

Could the internals of the pump have an issue? Not enough pressure? A leak between high / low pressure?
If this was fine before covid but not afterwards, what could have happened? I've never taken a pump apart - maybe shrinking seals?

Or something else?

I'm sorry if this is a bit long but wanted to give as much background as possible. It’s currently stuck on my drive until I can get it moving under its own steam.

Any help or advice very gratefully received.

Cheers

 

[lefty67]

Im no mechanic but do have an aaz engine. My cold start cable has never been connected. Shouldn't need it if glow plugs are good. I had a similar fuel related issue to you ie big air bubble in pipe. Source of much swearing and cost! Ie new fuel tank, hoses etc, turned out it was coming in through the pipes on the fuel filter. They weren't sealing properly!!

[Gavrilo]

The standard VW fuel filter can be a pain, try by-passing the thermo valve in the return to send the fuel back to the tank and not through the filter, put a piece of fuel line linking both hose tails on the thermo valve. If its not a VW filter ignore this.