Rotary 3B loosing prime over night

[cruiser_guy]

I've had to replace the engine in my BJ60 out here in Sierra Leone, West Africa https://forum.ih8mud.com/diesel-tec...ne-swap-some-little-village-sierra-leone.html . The only 3B's available were rotary pump models much newer than my old inline injection pump model.

The rotary injection pump has a return line that the inline pump does not have. I ran the return all the way back to the fuel tank return using a small fuel line (I have an FJ60 pickup in a long range tank).

With the old inline 3B there was NEVER a priming issue except of course when I was stupid enough to run out of fuel.

Since swapping the engine I have had an issue with loosing prime overnight. I first attributed it to a poor quality primer pump so I bought another one in country, also cheap. The problem remained. I ordered a Delphi primer pump and a non-return valve for the fuel line from England to get something better than the dime store quality Chinese junk sold in Sierra Leone. The non-return valve came and I installed it at the inlet to the primer pump. Still lost prime. The new Delphi primer pump assembly came and I am STILL loosing prime!

Once the truck starts it starts easy all day. The longer you leave it the longer you need to crank which makes sense as it does loose prime. The next morning I need to bleed the primer and crank for a bit to have it go. If I leave it for a few days it becomes a bigger headache. More priming and cranking.

Where to look now and how to find this air leak?

 

[canucksafari]

Charles, you are having a tough go of it. But no doubt, the outside temps there are more comfortable than they are here.

Those small leaks are the hardest to find because they will draw air but will not leak fuel that is pulled through. One solution is to fit an electric pull through pump near the tank. This will not only help the lift pump in your rotary IP; but also, it will pressurize the fuel line prior to the IP. Diesel should start to weep or drip where there is a small crack. I have also heard of people applying low pressure to the fuel system with compressed air from the tank filler hose. Again, fuel should start to weep or leak from a crack.

Do not discount the primer (even if it is new) or fuel filter seals and housing. My friend back east put in a new filter housing and had the exact same problem. He found it was weeping at the seal where the filter contacted the housing. The new housing had a very small crack through it. Another friend put cracks in his return lines (on both his Safaris) when he took the injector lines off to put in new injectors. It was kind of hard to see where it was weeping because that area was already damp with diesel from bleeding the injectors.

 

[cruiser_guy]

Maybe the best thing is to temporarily install an electric pump at the fuel pickup and later at the return and pressurize the system with the truck off. Can I mess up the injection pump by applying pressure to the return side? Is the pressure from the pump going to blow off hoses before I have a chance to see weeping?

I'm not really interested in having an electric pump installed permanently as it would not maintain prime anyways as it would not run all the time when the truck is off.

 

[canucksafari]

if the return was cracked, the pressure from the IP would make it weep. Just that it isn't easy to see if they are already wet with fuel from bleeding the injectors.

Quite a few people fit an electric lift pump close to the tank because it is supposed to help the longevity of the internal lift pump on a rotary IP. I think the magic PSI you want it 6-9 PSI at the pump. I've a friend in Australia who build's diesel yachts and also 4x4s. He tells me that it is very unlikely that a 14 PSI pump installed near the tank will deliver 9 PSI at the IP. Also, they rarely produce the PSI they claim right at the outlet. Even 14 PSI should not blow any hose off. I was told that higher than 10 PSI at the IP causes the timing to advance on a rotary pump.


If you get a pull through pump like a Walbro or one of these Airtex (AIRTEX Part # E8131 24V or AIRTEX Part # E8153 12V) your IP lift pump will still pull fuel even if the electric pump fails. The Walbro is supposed to be very quiet but I think is around $150. The Airtex pumps are $39.13 on Rock Auto. Summit Racing sells them for a bit more. Princess Auto also use to sell them. Not sure what you will find where you are. I know of one guy who says he has had an Airtex in his safari for the last 4 years without issue. Probably easier to find a Walbro where you are.

 

[roscoFJ73]

When I had an airleak,I refitted one joint in the fuel line with a new clamp in the engine bay per day.
On the 4th day I started on the return line from the pump at the pump end and next day it started perfect and was never a problem again.

It had no signs of seepage.It seemed to be syphoning itself back to the tank and emptying the fuel pump.
I guessed it was the one before I fitted the new clamp because when I removed it,it had no fuel in it.

It was also a case of the longer it sat,the longer it would take to start.It also got slowly worse over time.