97 Diesel Hard start and stalling when less than half tank.

[Condor]

I have been having an issue that is similar yet not exactly the same as a few other topics I've read on here so Ive decided to make my first post and see if anyone has any info that could save me some time.

I have a 97 bongo with the WL-T. It runs pretty great when the tank is full, but as the tank gets lower it starts to get symptoms of fuel starvation, especially when warm.

I can have some exceptionally hard starts. So far I have always been able to get it to start, but I really have to hold down on the key for an extended period of time before it coughs enough fuel into the engine to get started, then it will idle just fine. This starts to get dramatically worse when the tank approaches around half, and just gets worse as it gets lower.

I've also experienced the car stalling out, this happens when slowing down and stopping, and especially when the A/C is on. If I keep my foot on the gas while holding the brake to idle it higher, it will prevent this from happening and is also a very sketchy PITA.

When going up steep inclines this problem is accentuated and I have stalled out while driving in these situations, even with 2/3 of a tank.

Some threads suggested that it could be due to a clogged vent in the fuel cap. I have taken to removing the fuel cap when the tank gets low, which mildly helps but does not cure this issue.

The best idea that I have on this is that its a fuel pump issue. I have also read threads suggesting to clean out the filter inside the fuel pump, and/or replacing the fuel pump itself.

I'm wondering if anyone has any advice on how to properly diagnose this issue? Is the fuel pump the likely culprit? I have recently replaced the fuel filter so I doubt it is that. Also is there any other components of the ventilation system I should suspect?

Thanks a lot!!

[teenmal]

Have you cleaned the thimble type filter on top of the pump on the inlet , they call it the banjo filter, also check all vacuum pipes are connected.

[Northern Bongolow]

The fuel tank pick up pipe has a little thimble filter on the end inside the tank, this could be blocked or restricted a little. Take off the pipe that goes into the fuel pump and blow back to the tank, when clear try sucking back towards the pump to help it prime.
The tank itself also has a breather and one-way valve on it ,this is clipped on to the side of the tank itself viewed from under the van. The breather is about the size of a small cotton reel and just pulls off the tank then off the pipe end. Just inside the pipe end is also a one-way valve, remove and clean but note it's direction when refitting. It's like the ones used on windscreen washer systems to stop water running back.
Check the pipes that go into the top of the tank, they are susceptible to corrosion, you can check the rubber pipes and connections whilst in there. The short steel pipes on the top of the tank Sender etc can also rot usually where you cannot see them on the inside radius so check carefully.

[Condor]

Thanks so much to both of you. I’m going to see if I can get all of that done tomorrow and I will report back.

[Condor]

The tank itself also has a breather and one-way valve on it ,this is clipped on to the side of the tank itself viewed from under the van. The breather is about the size of a small cotton reel and just pulls off the tank then off the pipe end.

I checked banjo filter and it was clean. also pipes to the tank aren't corroded, also, Im curious if this is what you meant by the breather/ one way valve?

[Northern Bongolow]

That's one of the 2 valves which are at the end of that pipe. It's clipped on to the chassis, just pull it. Then remove it from the end of the pipe. Just inside the pipe end is a little thimble one way valve too. Clean em both out.

[Condor]

I removed and cleaned the valve inside the hose on the breather. It wasn't dirty and didn't seem to make a difference, I also ran the van with out that part on and it didn't make a difference.

I started to think that maybe the fuel filter could have something to do with this issue, I bought a clearview inline filter from an autoparts store and hooked it up to see how it would run. First time it started with no issue and ran really nicely for a while, but when I drove on it for a while the next day it started having the same issue, worse even. I also was able to note that there are a ton of little bubbles coming through the fuel filter. Would this mean I have air in my diesel from somewhere and this could be causing the issue?

Here are two videos I made of the clearview filter on a good start and hard start.

Good start:
https://youtube.com/shorts/CGHVrteNRpM?feature=share

Hard starts
https://www.youtube.com/watch?v=7D3cbDPHz3o