Suddenly won't start after recent tandem pump change

Hi @johnyfartbox ,
Did you replace the clip? The hose looks like you could chop half an inch off the end of it to get to a better bit of rubber?

PXL_20230327_160409131.MP.jpg20240407_204028.jpg
:)👍

Hope swapping the intank sender unit works🤞

Edit: answer to the question asked below is yes.
The hose and clamp are part of the return line from the lower part of the tandem pump (out feed).
 
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Interesting, I will check that out today, that's the outfeed pipe isn't it,
Something I've found out while pulling and pushing these pipes off and on is to use a heat gun to slightly warm the rubber up, not too much but it helps.
 
Another day, another theory.
Is it possible to remove the sender assembly, and put it, complete with connections, in a shallow bowl of diesel, and watch what happens? That would mimic normal operation.
By varying the height of the bowl, the effect of uphill and down hill parking could be checked too.
Mac.
 
Reading back through the comments in my thread, it seems that there definitely shouldn't be air in the return line, so the fact that you were getting air in the return line when you did your diesel purge, would seem to be of some concern.

I would think it would have to be coming from either bad fitment of the tandem pump, or the injector seals. I'm sure it's been said more than once that bad injector seals produce pretty much the same symptoms as you have been getting, so that is maybe something to consider.

If it does rain all day tomorrow as forecast, I might take the injectors out on my spare engine and have a look at these seals to get an idea of what is going on.
 
PlasticMac said:
Once the fuel supply enters the pump, it is pressurised, so pressure side a leak would be visible, I think.
Air is separated out by the mesh, and passes via the tiny restrictor to the return, where you're see it.
Air is only separated by flow through the mesh, and on idle, most of the flow will be straight into the return, which doesn't pass through the mesh, so the volume of fuel actually going to the injector circuit is small. To me, that means it'll take quite a while to purge all of the air in the pump.
@rotifer is right, check the bubble size and flow rate. Hopefully, it will reduce, 🤞
Mac.
Edit: Long time ago now, but this saga started with a tandem pump replacement, all was well till then so things like injector seals seem unlikely to be a problem now.
Click to expand...
Just re read your post.......The tandem pump was changed because the car was always a hard start when facing uphill so suspected the pump.
It now might be a possibility that the LUK pump was ok.
I kept the old pump.
 
DaveySprocket said:
Reading back through the comments in my thread, it seems that there definitely shouldn't be air in the return line, so the fact that you were getting air in the return line when you did your diesel purge, would seem to be of some concern.

I would think it would have to be coming from either bad fitment of the tandem pump, or the injector seals. I'm sure it's been said more than once that bad injector seals produce pretty much the same symptoms as you have been getting, so that is maybe something to consider.

If it does rain all day tomorrow as forecast, I might take the injectors out on my spare engine and have a look at these seals to get an idea of what is going on.
Click to expand...
If the non return valve in the return fails the return line might never fully purge. The flow rate of the pump will not be be massive, (the injectors need high pressure, but not much flow, just one squirt at a time, and with no nrv, the flow in the return could be high enough to drop the pump pressure near to zero. Low flow = high pressure, e high flow = low pressure.
Could the white stuff be very aerated diesel, due to the pump rotor cavitation, at low pressure?
Mac
 
Here's the whole of the pump description, posted by @Joga
If this pump, from a 1.9 is similar to the A2 tandem pump, there's a bit more to it than we thought, particularly with the return.
Mac.
Screenshot_20240408-174553.png
 
Yesterday I decided to check the short feed pipe to the pump and did a fresh reconnection making absolutely sure that the pipe was completely air tight.
I also did the same with the return pipe with the temperature sensor mid way by disconnecting the sensor and checking the O ring in the housing, it all looked ok but I added a small amount of HYLOMAR BLUE FUEL RESISTANT SEALANT, it was only a tiny amount just to help with sealing incase the O ring was worn, put it back in place and having the pipe in my hands made sure that it was pushed well in place and the green horseshoe clip was well and truly clipped into place.
I also trimmed off around half an inch at both ends of the pipe and used fresh single ear pinch hose clamps . There is enough length of pipe to do this without the pipe becoming to short.
So, happy with that, I made room to enable me to get to the four bolts that holds the pump to the side of the engine, I had previously tourqed up the top two to 20nm and the bottom two to 10nm as advised.
Using my new torque wrench at the above settings I found that each bolt tightened up very slightly to each setting thus making me think that the bolts had undone ever so slightly or my old wrench was not calibrated.
Any way, all put back together and also the fact that fuel would now need to be pulled back up into the pump due to pipes being removed I expected it to take a few cranks to fire up, I was pleasantly surprised that the car started after two twists of the key with a slight difference in tickover until fuel was being fed into the pump.
It happily ticked over for a good 15 minutes until I stopped the engine.
That was last night around 6.30 so packed everything away and at the moment I've not yet tried to start the car as yet, I'm going to have some lunch and try it again in half an hour and report back.

Fingers crossed eh?
 
If you still get air in there here are some suggestions:
The clip is not fully crimped, red arrows
There looks to be a crack in the pipe, could let air in. yellow circle.

A2 leak.jpg
 
Ok lads, I decided to skip lunch, grab the keys and try and start it.
Little Dog said:
If you still get air in there here are some suggestions:
The clip is not fully crimped, red arrows
There looks to be a crack in the pipe, could let air in. yellow circle.
Should the clip and pipe be to the left of the bulge in the pipe? It is raining so not taking the bonnet off to check mine, green arrow.

View attachment 122109
Click to expand...
Fair comment.
This is brand new tubing, not the old.
I can't squeeze the clip any more than that I'm afraid but I did read that you shouldn't do that anyway.
 
They look the muts nuts, the type I have are just pincers with longer handles. I'll check out those in the photo
I take it you need something to turn the thing on the left to wind it in? The problem I see with that setup is being able to use it in tight spaces.
 
Video here lads

So there you have it.
Listening back to the video I now notice that there was a slight struggle on first twisting the key to start the car, I didn't allow the glow plug light to go out, not sure if that would effect the initial start up.
But other than that, you can see and hear that the engine has no problems running and reving, though that's always been the case when the car managed to start.
 
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I've just been back to the car and it started again, but again there was a slight half second struggle before it fully ran smoothly.
Maybe the very slight what seems like fuel starvation is still there, but it's no where near as bad as it has been in the past, I suppose the real test is overnight with the car up at the front.
Lets see.
 
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