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4jb1t / 4jg2 injection pump questions

Getting the best performance from your Isuzu, the in's and out's

4jb1t / 4jg2 injection pump questions

Postby kg4pam » Tue Dec 25, 2018 1:35 am

Good day and Merry Christmas! I've been lurking here for quite some time- at least 5 years or so. I am in the US. I converted my 1981 Jeep CJ-7 to a 4JB1 way back in 2013. I also converted a US market Trooper to a 4jg2 around the same time frame. The engine has been perfect in the Jeep, perfect balance of power and economy. I sold the Trooper, but last I heard it was running well!

Recently I've noticed a small leak from the injection pump. It appears to be coming from the cover (related to the absent cold start device?) circled in red:
pump leak red.png


I've replaced the o ring, to no avail. I'm going to remove the cover again and dress the mating surface with some 400 grit paper and a plate of glass. Any ideas of what to do if that doesn't fix the issue? it's only a very small drip, so i'm not TOO concerned.

That brings me to the second part of my question. I have a spare injection pump from the Trooper/4JG2 build that I would like to recondition and have ready to swap onto the Jeep so as not to have a lengthy downtime:
pump overview.png


Here is the dataplate on the pump:
dataplate.png


And here is the biggest downside to the whole deal:
broken delivery valve holder.png

The holder broke off during shipment to the US from the UK, and the mangled mess is where I tried to remove the broken off 'stub' from the rotor head.

Is there a way to convert this pump from 4JG2 to 4JB1? I have done some reading, and it appears that the rotor head and delivery valves would need to be changed out. Which of course I have to do anyway due to the broken holder issue. Is that all I would have to change? Does anyone have the correct part numbers? They seem to be plentiful on AliExpress and even ebay. What all matters for the rotor head? Can one for an industrial 4jb1 (skidsteer, forklift) work in a vehicular application? I think I recall some of those spinning in reverse though.

I also need a source for the delivery valve holders as i have searched and searched and not come up with an ecommerce site selling them.

I have the Bosch O-ring kit and would like to tackle re-sealing the pump myself. I don't have anything to lose, and there is a pretty good build thread floating around the internet for a VW pump (still a VE style) build.

So, in summary:
1) Is there a sure fire way to get the cold start cover to stop leaking?
2) Can an injection pump meant for a 4JG2 be converted to work with a 4JB1?

Thanks a million for reading this post and for any assistance you can provide.
Merry Christmas and happy New Year!
~J
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kg4pam
Isuzu Baby
 
Posts: 5
Joined: Sat Sep 09, 2017 3:43 am
Age: 37
Country: United States
City: East TN
Vehicle: 1981 Jeep CJ-7 with 4JB1-TC.

Re: 4jb1t / 4jg2 injection pump questions

Postby kg4pam » Thu Dec 27, 2018 11:02 pm

Well I found the solution to one of the issues and feel a little sheepish about it. As it turns out, the cover that leaks is the one on the side of the pump closest to the engine, not the one I circled in red. it was seeping, draining over the bottom of the pump, and dripping off the cover that I worked on. So now the next step is to replace the o ring on the inner cover. (which of course either means some delicate surgery or removal of the pump)

As for reconning my spare pump, the part numbers seem to match up for this rotor head: https://www.aliexpress.com/item/T-DI-Di ... 49809.html so I'll probably order it at some point.

I'm still looking for the delivery valve holders if anyone has a source for them.

Thanks!
~J
kg4pam
Isuzu Baby
 
Posts: 5
Joined: Sat Sep 09, 2017 3:43 am
Age: 37
Country: United States
City: East TN
Vehicle: 1981 Jeep CJ-7 with 4JB1-TC.


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