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TR8 Cranks won't turn over

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TR8 Cranks won't turn over
#1
  This topic is about my 1981 Triumph TR8
erictr6 Avatar
erictr6 eric l
Denver, NC, USA   USA
Happy New Year!
Today was our club President's Drive. Went to start the 8 and the starter would crank strong but not turn over and start.
First attempt was to reset the inertia switch, dizzy rotor ok, next checked voltage on battery - 12.77v, gas gauge reads over quarter tank, removed the AFM to confirm the flapper was not stuck disconnect and reconnect a few injector plugs, can smell fuel from under the plenum, must be getting gas, ,, disconnected and reconnected the ECU multi point connector. Nothing would make it turn over and run. My neighbor stops by during the middle of this routine and says, do you have spark? Yes. Finally decide to confirm spark, removed #5 plug and place the end to the strut bolt. Turn the key, started and ran on all 7 cylinders. Reconnected the plug, tried one more time and guess what.............................it cranked strong, turned over and ran!!??
Missed the President's run.....at least it works. Question is why?

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Cheapsnake Avatar
Cheapsnake Tom Soik
Sturgeon Bay, WI, USA   USA
It's an obvious case of your kinipling shaft being out of sync with the muffler bearing, a common problem in the 8's. The factory service manual prescribes a gathering of gearheads standing around and scratching their heads as the problem fixes itself.
Seriously though, randomly occurring problems that seem to fix themselves are the most frustrating issues to diagnose. My best guess is that you flooded the engine (yes FI engines will flood) and the time you took to diagnose the problem gave the engine time to clear itself. Just a guess. Good luck.

erictr6 Avatar
erictr6 eric l
Denver, NC, USA   USA
At what temp does the cold start injector kick in?
Are they available?

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Cheapsnake Avatar
Cheapsnake Tom Soik
Sturgeon Bay, WI, USA   USA
I can't answer your question about cold start injector temp kick-in, but I think you're on to something. If the ambient temperature and/or your engine temperature were just on the margin where the cold start injector wasn't needed, but the injector was programmed to kick in anyway, then you have a flooding condition. This is why I've always hated automatic chokes. If that's the case, the solution (hopefully) is identical to carbed cars, hold the gas to the floor and crank. The other option is to do just as you did and pull a couple plugs, dry them off and hope it's enough to fire things up. Hopefully, you'll never have to test either of these options.

erictr6 Avatar
erictr6 eric l
Denver, NC, USA   USA
All,
Brought the car in to Glenn's MG (works on all LBC) for service and advised him of the situation last weekend. Guess what...no problem starting the car even after multiple attempts. Also checked the cold start injector and it's working. So much for now, will wait for the next event.
Thanks for your input.

darrellwalker Darrell Walker
Vancouver, WA, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
Glad you got it going. The cold start injector is controlled by the thermotime switch, so if you suspect the injector in the the future, that switch could also be the problem. The switch is controlled by coolant temp (thermo), but also has it own heating circuit (time). I never saw much difference with or without the injectors. I don't know the exact temps, but if you engine is at ambient temps, I think it should fire the injector at least a short time.

Another issue I had with mine was the spark plugs. I installed Bosch platinum plugs, and all was find for 6-8 months, then it got very hard to start cold (either first start of the day, or after sitting all day at work). Once it fired up, restarting was no problem. I went through everything in the ignition and FI system multiple times, until I finally decided to put the old crusty Champions in. Solved the problem immediately. I couldn't see anything on the Bosch plugs that looked off, but I showed them the inside of my garbage can!



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, OR, USA   USA
1980 Triumph TR8 "Wedgie"
In reply to # 1505853 by darrellwalker Glad you got it going. The cold start injector is controlled by the thermotime switch, so if you suspect the injector in the the future, that switch could also be the problem. The switch is controlled by coolant temp (thermo), but also has it own heating circuit (time). I never saw much difference with or without the injectors. I don't know the exact temps, but if you engine is at ambient temps, I think it should fire the injector at least a short time.

Another issue I had with mine was the spark plugs. I installed Bosch platinum plugs, and all was find for 6-8 months, then it got very hard to start cold (either first start of the day, or after sitting all day at work). Once it fired up, restarting was no problem. I went through everything in the ignition and FI system multiple times, until I finally decided to put the old crusty Champions in. Solved the problem immediately. I couldn't see anything on the Bosch plugs that looked off, but I showed them the inside of my garbage can!

Darrell:

By the way, do you have a brother named Darrell? (Referring to the old Bob Newhart show) eye rolling smiley

OK, back to the topic at hand. I have had similar experiences with "new and improved" spark plugs. I had some platinum tipped plugs supposedly good for 100,000 miles in my Z-28, but the platinum tips kept falling off, resulting in plug gaps through which you could drive a Volkswagen. Tossed those and went back to plain old Champions. Also wondered what the errant platinum bits did to my motor as they passed through. <sigh>

The multi electrode plugs are a waste, because only one electrode fires at any given time.

Splitfire plugs are defunct having been sued by several state attorneys general for wildly overstating the benefits of the design. "Improved Mileage and Power" indeed.

With almost everything else having been changed since the development of the internal combustion engine over 100 years ago, the spark plug is virtually unchanged. There is a reason for that; it is very good at what it does, and there is little if anything that can be done to improve it.

Important tip for forum members: Save your money and buy only plain vanilla spark plugs.

Vance



1980 Platinum Metallic TR8, navy blue interior
Bare metal respray, Crower cam, raised compression
ported heads, modified Zenith carbs, 0.060" overbore

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darrellwalker Darrell Walker
Vancouver, WA, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
In reply to # 1505862 by Darth V8R Darrell:

By the way, do you have a brother named Darrell? (Referring to the old Bob Newhart show) eye rolling smiley

Vance

Nope, and I don't have a brother Larry, either! smiling smiley



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA



Edited 1 time(s). Last edit at 2018-01-04 04:52 PM by darrellwalker.

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