3B Rotary Pump timing adjusted by PO to 13BT specs--Advice Please!

[aboisvert]

I have a new to me 1985 JDM73 with a 3B rotary pump. PO wanted more power, so he bought a turbo kit from someone on MUD (NOT Diesel42) and installed it. He figured he would be extra smart and he researched where the pump timing was set on a 13BT, and he then altered the timing on the 3B pump "by a little bit" to match the 13BT timing spec. He did this without driving the vehicle after the turbo install. Everything was done in one session. He said he used a probe tool that somehow measures the internals of the pump (or something like that). He had experience timing VW diesels and said it was similar, and seems confident he did what he was trying to do.

So he has no idea if the timing adjustments made any difference either positively or negatively.

He never adjusted the fueling. Just drove it. I got it, and it feels underpowered from where it should be. So I added some fuel and it's a little better. Now I get a some black smoke if I floor it but it's nice and clean at idle.

I never get above 600 on the pyro after adjusting my fueling. And it struggles to reach 10 psi of boost.

So, my questions are this:

Should I endeavor to put the 3B pump back to stock timing settings or leave it alone set where he said matched the 13BT timing specifications? If so, how do I do it? I did some searching but don't see stuff about the rotary pump, only the inline pump. Has anyone attempted to do what he did and can give me help to "undo" it if the timing change is still causing the lack of power?

It's drivable the way it is, but I know that a properly Turbo'd 3B can be a better. And I want to give Diesel 42 a big shout out. I thought the kit on the truck was his, and even after we realized it was not one of his he has spent time on the phone with me looking at it. Great guy.

I understand that my turbo may not be a perfectly engineered setup...and it may be doing exactly what it's supposed to be doing which is just not as optimal as Diesel42's kit. So I'm looking to learn if the pump timing adjustment could be an issue. If its' not an issue, I may decide to buy a Diesel42 kit and sell this one in hopes of improved performance.

 

[Eurasiaoverland]

The 13B only ever came with an inline pump, which is spill timed, so I've no idea how the PO would have re--timed the 3B pump to 13B-T specs.

If you can see the match-marks on the timing case and injection pump flange, just line them up. The pump is not very sensitive to static timing. Get a 1988 or 1995 Factory Service Manual for the 3B if you want to understand rhe full procedure. This is technically a later engine, (aka the 3Bii), but there will not be an English manual for the old 3B (pre 1988) with a rotary pump, as this was only made for the JDM.

 

[Gubbtratt1]

3B is indirect injection, 13B-T is direct injection. I'm not 100% sure, but I believe an IDI wants earlier injection, and adjusting it to DI specs would make it fire too late.

 

[aboisvert]

The 13B only ever came with an inline pump, which is spill timed, so I've no idea how the PO would have re--timed the 3B pump to 13B-T specs.

If you can see the match-marks on the timing case and injection pump flange, just line them up. The pump is not very sensitive to static timing. Get a 1988 or 1995 Factory Service Manual for the 3B if you want to understand rhe full procedure. This is technically a later engine, (aka the 3Bii), but there will not be an English manual for the old 3B (pre 1988) with a rotary pump, as this was only made for the JDM.

Thanks so much for the help. I will have a closer look to see if I can find the timing case and pump flange marks. Hopefully I can find them, I did not know they existed.

Thanks for the info about the 13B pumps, I'll run that by the PO and see if he even recognized that....or if he was mistaken in what he told me originally.

 

[aboisvert]

3B is indirect injection, 13B-T is direct injection. I'm not 100% sure, but I believe an IDI wants earlier injection, and adjusting it to DI specs would make it fire too late.

Thanks. If i can't find the marks at least this gives me an idea on what direction to go if I have to guess! If you've ever done one, any hints would be great! I'll try to find an FSM for a rotary 3bii.

 

[Eurasiaoverland]

Here is the plugner stroke specification for 3B (IDI, NA), 14B (DI, NA), 15B-F (DI, NA) and 15B-FT (DI, turbo) engines.

Plunger stroke is a proxy of timing; higher stroke means more advance. There is no clear relation to injection type (IDI vs DI) so I've no idea what the PO might have imagined a 13B-T stoke would be, if it had a rotary pump, which it never did. For reference, the 14B-T and 15B-T (both DI, turbo) have a plunger stroke of around 0.94 mm from factory.

I assume what the PO meant is that he advanced the timing to try to get more power out of the engine. See this thread for more info: downside of advancing timing?? - https://forum.ih8mud.com/threads/downside-of-advancing-timing.520211/

Remember that a 3B was never designed to be turbocharged, and excess heat is the enemy for the weak IDI heads.