Full throttle or nothing

[Sapper]

Hello. We had taken the MD17C out of our Albin 25 this past winter to do the seals in the engine including the timing cover and injection pump. Upon reassembly when we start the engine it seems to run at full throttle (or close to it) or nothing. The control cable is disconnected and we are using a flat top screwdriver to adjust the throttle once it starts. Basically it starts at full throttle and when you adjust to the idle position it shuts down. We have checked the linkage from the throttle shaft to the control arm on injector pump and it seems ok..but we are certainly not experts. We have changed out injector pumps and nothing. Anybody have any ideas? Thanks.

[WillieC]

You have the book right? Assuming it’s the same pump going back in the same hole. The gasket underneath the pump is critical for timing. A trick was making sure the pin link inside is all aligned before mating the pump to the case.

Also is the external oil line connected? It comes from down by the tach sender and routes up and over the governor housing. It is part of the cold start circuit. It allows the rack to advance to full throttle and needs to be working to limit the travel as soon as oil pressure comes up.

It’s all in the manual but it’s a little tricky.

[Sapper]

Thank you WillieC. We were just wondering yesterday why that oil line came across. At the moment we are at a standstill as the spring that pulls the rack has broken. We are trying to source one but no luck so far. We may have to make one but we are worried about the tension.

[WillieC]

Yes, that tension is important, but it is a spring, not a microprocessor. That would certainly send you to full throttle. It works in conjunction with the governor, which is another whole issue. Your's sounds like it is working.

If you have the broken spring in hand, you can get close but finding a junk shop...try the hardware store first. Find an old mechanic. Typewriter?

Good luck. Keep us posted.

[Sapper]

Thanks. I may do a post on here to see if anyone knows where I might find one. We are in a small costal community here in Newfoundland. Not a lot of resources locally.

[WillieC]

Two minutes searching this morning:

18 Tension Spring 833081 1 - Thru Dealer**

from:

https://www.volvopentastore.com/Governo ... _id.771938

Now this needs more verification and you will need to contact a VP dealer, but here is your part. It looks to be still available.

It might cost fifty bucks...

Further, I have been pondering this. The spring holds one lever against the high rev limiter pin. When you request full throttle, you don't get full throttle, only what the governor lets the rack travel. I may be over-simplifying and describing any setting less than full throttle. But the principle is correct. This is why the screw adjustment behind the cover is critical. It limits the travel of the rack at full throttle. One of my repair attempts on the MD17C, I set that stop way too far. It let the rack dump fuel into the injectors way more than the engine could handle and I coked it up badly in one season. Full top end dismantle required.

The Idle, low speed adjustment is not simply moving the visible throttle cable stop on top of the governor housing, like you might on a 1957 Volkswagen. The adjustment is to be made by rotating the vertical control rod held by the locknut, thus "by request" shutting down the injection pump rack. It may sound goofy, it is not intuitive, and truly these adjustments can and should be made once the engine is up and running and at operating temperature, which you haven't by your accounts achieved just yet.

Just trying to help here. The book tells you what to do, and how, but leaves out the "why". Still you need to have it on hand.