13 replies to this topic

[sdjones121]

I have a 1987 Mini Advantage with a 1275 out of (what I understand was) a 1985 MG Metro. It went into climate controlled storage in late 2017 and I just got it back a couple weeks ago. Prior to storage it tended to run a bit rich, but nothing crazy. While in storage it was occasionally started and allowed to idle for awhile, but was rarely ever driven out on the road; a friend was graciously storing it for free while I was abroad, so I can't complain too much.

 

Since I got it back it starts fine but it was immediately clear that it was running extremely rich, like black plumes of smoke when I hit the throttle rich. I haven't done much just yet, I know I need to do a valve adjustment and check the timing, but I was hoping to at least lean it out a bit to stop spewing black smoke whenever I have to let it run. Last night I hooked it up to my Gunson Gastester, which I know is a deeply fallible instrument but I wanted to at least try and get it into the ballpark of a good AFR, and I discovered that no matter how I adjusted the mixture screw on the side of the HIF44, the Gunson never changed, and there was very little change to the idle (which I had set at about 950). Similarly, the black plumes were the same no matter where the screw was. As you might expect, the plugs are as black as night. Looking at the car again tonight, I noticed the oil absolutely has fuel in it.

 

In terms of past work I've done, it's pretty minimal as it's always been pretty reliable. I had to replace the fuel pump, which I did with another mechanical one, about 7 or so years ago, I needed the tropical fan and a new radiator about 5 years ago, but that's about it. I've had it since 2012. As I said, I know I need to do basic tune-up stuff before I dig in too deep, but the fact I couldn't get it down from its super-rich mixture was pretty concerning. That said, I wanted to throw it out there and see if this issue immediately brought anything to anyone's mind, especially in light of two years of storage. Things that I have considered are a carb service kit, getting a compression test kit and using it, and valve seal replacement. But obviously I don't want to just shotgun parts at it.

 

Any advice is greatly appreciated!

 

EDIT: Found some older posts regarding somewhat similar issues and a couple of them pointed to the o-ring on the choke, so I popped mine off. As you can see in the image it's...terrible. I have to imagine every other service item in the carb looks about the same.

 

 

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Edited by sdjones121, 07 October 2020 - 12:56 AM.

[Dusky]

Carb needs a rebuild at this point. Probably no need to touch the valves etc .

[sonscar]

As said carb rebuild,the float could be flooding.Steve..

[cal844]

You say you have fuel in the oil, is the car fitted with a mechanical fuel pump, the seals will be shot.

Fit a carb service kit

[sdjones121]

You say you have fuel in the oil, is the car fitted with a mechanical fuel pump, the seals will be shot.

Fit a carb service kit

Yeah, it has a mechanical fuel pump, I replaced it a year or two after I got the car. Which seals are you referring to?

I’ll be ordering a carb service kit today.

[cal844]

You say you have fuel in the oil, is the car fitted with a mechanical fuel pump, the seals will be shot.

Fit a carb service kit

Yeah, it has a mechanical fuel pump, I replaced it a year or two after I got the car. Which seals are you referring to?

I’ll be ordering a carb service kit today.

The diaphragm in the pump, it sounds like it could be holed due to Ethanol on the fuel

[sdjones121]

Got it, thanks. I assume there is no way to test that, and I just need to swap it, correct?

Thanks all for the advice, I’m ordering parts today. First carb service I’ve done, so wish me luck!

[Ethel]

I reckon you've answered your own question. The choke's totally separate on Hif's, so when they fail they have a big effect.

 

You might have to buy a service kit to get a new O ring though. The only other bits that tend to wear are the float pivot and float valve - and the throttle shaft bushes, but that'd make it run lean.  

 

 

Pump diaphragm failure is pretty rare and would be likely to cause lean, not rich, running from lost fuel pressure. The fuel would escape in to your sump, which you certainly don't want! However a whiff down the oil filler/ dipstick should give it away. If you were really paranoid, you could rig up a flow test with some hose & jars while cranking the engine. If the diaphragm is good fuel out = fuel in.

[richmondclassicsnorthwales]

AUD3602 is the part number for that little O ring on the choke mechanism

[sdjones121]

I reckon you've answered your own question. The choke's totally separate on Hif's, so when they fail they have a big effect.

 

You might have to buy a service kit to get a new O ring though. The only other bits that tend to wear are the float pivot and float valve - and the throttle shaft bushes, but that'd make it run lean.  

 

 

Pump diaphragm failure is pretty rare and would be likely to cause lean, not rich, running from lost fuel pressure. The fuel would escape in to your sump, which you certainly don't want! However a whiff down the oil filler/ dipstick should give it away. If you were really paranoid, you could rig up a flow test with some hose & jars while cranking the engine. If the diaphragm is good fuel out = fuel in.

 

Do you think it's worth it to just replace the o-ring first instead of doing a full service kit to see if that fixes my issue?

[Ethel]

It could well be, it could easily have swollen & stuck from standing, not really applicable to other carb parts, but old fuel can gum things up.

 

Your call really, they're all relatively cheap bits. Could be the postage & inconvenience is more given where you're located. If you don't need it fixed in a hurry you could  investigate the state of the float valve etc before ordering, the bottom cover usually comes off without needing a new seal, but you might well need a new gasket or two if you remove the carb.

[richmondclassicsnorthwales]

It is a worth considering how many miles you have done with that particular carb

 

There are little filters in the 44,s where the fuel goes in. Needles do also have a habit of just literally giving up the ghost, then petrol just pumps out the carb. The tip of the needles just wear.

 

There is the expression, if it ain't broke don't fix it, but personally, if it has a good few miles on the carb, and you are keeping the car, then do the job as an all in one with a new O ring too. They're not the hardest job to do, but I know where your coming from with just replacing the stepper ring

[sdjones121]

It is a worth considering how many miles you have done with that particular carb

 

There are little filters in the 44,s where the fuel goes in. Needles do also have a habit of just literally giving up the ghost, then petrol just pumps out the carb. The tip of the needles just wear.

 

There is the expression, if it ain't broke don't fix it, but personally, if it has a good few miles on the carb, and you are keeping the car, then do the job as an all in one with a new O ring too. They're not the hardest job to do, but I know where your coming from with just replacing the stepper ring

 

Ok, that makes sense. I'm going to try just the o-ring for now and add the full service kit to the to-do list. If the single o-ring gets it to where I can at least get it on the road and registered, that's a good start. I haven't a clue how many miles are on the carb, but I suspect it's a high number. Between multiple owners and and engine swap, the car's history is largely a mystery. 

 

Thanks again to everyone for the help! I'll post an update for posterity once I get the o-ring swapped out. 

[sdjones121]

Sorry to necro-thread my old conversation, but I always hate it when I find a discussion about an issue I’m having that doesn’t list the ultimate answer.

I did end up replacing just the choke o-ring, which, upon examination, was just a dried bit of black gunk. However, it didn’t fix the issue. Considering the terrible nature of that one o-ring, I assumed the rest of the seals were equally shot so I did a full rebuild. I’m happy to report it’s running great now and that the mixture is as adjustable as one would hope.

While I completely trust the advice in this thread about just replacing the one o-ring, in my case, every part of the carb was so old that it needed a full rebuild.