ummmm what the heck is wrong with my car?

[ThePharmacist08]

When I go turn to off the TR6 after riding for a little while, the engine bucks like a maniac. I feel like the engine is gonna break loose and jump out of the engine bay. The entire car shakes violently and sometimes starts right back up shakes some more then finally shuts off. After each time there is this really weird smell, almost like a fruity deisel gas smell after the car has shut off. Ive tried many ways of trying to turn the key and sometimes I end up having to just let the clutch out and purposely stall the car. My dad said his old MGB sometimes did that but not that bad (mind you he knows nothing) he used the term "deiseling". Car runs mint but just wont turn off nicely. Thanks everyone for answering my questions, im quite the noob to the "sport" ha. Mike

 

[RonMacPherson]

What year, what fuel octane are you using, what is your timing set to?
Oh, and what is your idle speed set to?

 

[TR3driver]

Sounds exactly like "dieseling", aka "run-on". Your anti-runon solenoid is not working.

That's the gizmo hanging on the bottom of the carbon canister, that is supposed to be energized only when the key is turned off but the engine is still turning (has oil pressure). It gets power from a special contact on the ignition switch; and is grounded through the third terminal on the oil pressure sender/switch on the side of the engine block. It should apply manifold vacuum to the carbon canister, which in turn should be linked to the float bowls through a valve operated by the throttle linkage on each carb. The vacuum sucks the fuel out of the jets, ensuring the engine gets no fuel to burn.

Lots of things to check there.

Or, you could do as I do, and just get in the habit of killing the engine with the clutch as you shut the key off. Don't wait for it to start dieseling, just leave it in gear (4th is better) and smoothly let the clutch out as the engine rpm drops off, while keeping your other foot firmly on the brake. Takes a little practice to do it smoothly.

The additional wear on the clutch is very minimal (the engine can't make any torque to speak of at that point, you're just taking momentum out of the flywheel) and it won't hurt anything else at all.

 

[Tinster]

Hey Cuz!!

Now, don't THAT line of questionin' bring back the memories??



Tinster the know-nuthin TR6 guy

Now Randall !! I'll not permit youz expert wrench guys to recommend
any slacker procedures...... after the torment, busted knuckles I been
paced thru for 2 1/2 years now, plus buying almost every Craftsman auto tool known to mankind.

"Let the clutch out", indeed!!!!!!!!!!!!!
Go to your room
now!!

d

 

[RonMacPherson]

Not all year 6's come with anitrun on valves. That was why I was hoping to get a little more information.

He IS describing classic runon, which is probably due to a faulty operation of an antirun on valve. but could be something simple like a loose wire ont he oil pressure switch.

But we need additional info to try to remote diagnose.

 

[Brosky]

Why don't we get together and I'll look at your settings for you? It sounds like a combination of things that can be adjusted to fix the problem.

 

[ThePharmacist08]

Good lord Randall that was an amazing response, thanks! Yeah I remember the local Triumph shop telling me my Anti-runon system wasnt hooked up correctly but that it was at least vented and not to really worry about it. Good to know i'll try the 4th gear clutch maneuver, then maybe attack the root of the problem. Thanks again, mike

 

[tomshobby]

Sorry, posted this in the wrong thread.

 

[ThePharmacist08]

Yeah Paul that would be great, sorry I couldnt make BBTS but i had to reschedule my graduation party for that sunday. Know any places for a good cruise, narragansett is amazing this time of year. Let me know what kind of schedule your on maybe we could meet up somewhere. Mike

 

[vettedog72]

Sounds like a job for Marvell Mystery Oil. Run through a full tank of gas with a qt of the Mystery Oil. If not improved, do the first part of what TR3Driver said.

 

[poolboy]

Ok now i've got it figured out, Tom. That is why that picture of the float chamber vents showed up in a 6- pack post.
I bet Shirley had you distracted, huh?
https://6-pack.org/modules.php?name=Forums&file=viewtopic&p=40705#40705

 

[Brosky]

I know that I'm a nut about picky details and I also know that Randall is a perfectionist. I generally agree with nearly everything that he says because it's always good solid advice, but the one thing that I can never get myself to agree upon is shutting of a car by stalling it.

I think that we can fix your problem without having to resort to the stall method. I'll get back to you when I know my schedule for the weekend a bit better.

 

[TR3driver]

Not all year 6's come with anitrun on valves. That was why I was hoping to get a little more information.

He IS describing classic runon, which is probably due to a faulty operation of an antirun on valve. but could be something simple like a loose wire ont he oil pressure switch.

But we need additional info to try to remote diagnose.

No worries, Ron, I agree with all that.
But the ARS started in 73, and continued through the end of 76 (for US-spec TR6), so a 75 should have it.

And I wasn't trying to remotely diagnose the root cause, just giving an outline of how to find the surface one. If it wants to runon every time, IMO there is likely something else wrong besides the ARS not doing it's job.

Another way to get them to want to diesel a lot less, is to disconnect the vacuum retard and readjust the idle without it. Use the "static" timing value from the book (something like 10 BTDC, don't recall offhand for a 75 TR6 and it varied by year).

But my TR3A (which had no ARS or canister or anything) would want to diesel sometimes (usually when underhood temps were unusually high, causing borderline percolation in the carbs), so I killed it with the clutch for many years.

Tinster, I've been "making do" with old cars since I was a kid. There's things I've gotten away with that I won't even mention in public.
<span style="font-size: 8pt">Hopefully I'll be dead before anyone else finds those shims.</span>

 

[poolboy]

<span style="font-size: 8pt">Hopefully I'll be dead before anyone else finds those shims.</span>

So it was YOU !! Just kidding, but have you ever been so desperate to make it home that you cut the tongues out of your shoes and used them for rod bearings? Morris Mini, Ville Platte, La. 1970.

 

[Brosky]

Mike,

I just looked back at some pictures of your engine and I see about five potential problems (that can help promote your dieseling issue) which be easily fixed once we get together. Did you get that air filter issue corrected so that you have a real working filter under there? That you can do and I'll bring a timing light and some other things for the rest.

 

[jjbunn]

I have exactly the same problem with run-on, and I have no emissions gear at all on my '71. I also suspect my timing is off, certainly my idle speed is too high ... so this post and answers resolved me to pop checking that to the top of my to-do list!

 

[ThePharmacist08]

Yeah paul I got the filters on their right now, so I can actually drive it anywhere.

 

[AltaKnight]

Run on is generally a product of carbon build up in the combustion chambers which glow when the engine is hot and reignite the fuel mixture (with poor timing I might add) after the ignition is switched off; left to it's own devices it can be destructive.

The anti-run on equipment (if your car is so equipped) is supposed to stop this but I don't have a whole lot of faith in it.

It can also be caused by ...
1)wrong type of spark plugs
2)ignition timing maladjusted
3)valve timing incorrect
4)too high an idle speed
5)poor quality gasoline/low octane
6)poor mechanical condition issues
7)other stuff I can't think of right now

So how about getting busy and answering the questions above particularly 1,2,4 & 5 and then we can sleuth it down.

Or you could kill it in 4th gear

 

[Silverghost]

I am seeing this similar thread in the other forums here, people experiencing run-on lately. Could this be caused by the "summer" "gas" blend many cities around the country are selling these days? Higher amounts of ethanol, etc? It seems to be a larger picture issue than just one or two or three cars being out of tune.....

 

[Guest]

The gas - that explains why my car took 2 whole seconds of cranking to start yesterday. (sorry - couldn't help it ).

Seriously, on carbs both with and without the canister, mine never dieseled. It was a bugger to start when it got colder than 50 degrees, but it never had any trouble stopping...