> My mechanic has been trying and failing to fix a persistent
> mis/back-fire on my TR6. Have changed or fixed everything he can think
> of, he reckons that it may be a cracked valve seat. The car pops and
> spits a few times when it's cold, then idles unevenly, and no. 2
> cylinder is apparently cooler than the others. Other than that it seems
> to be fine. Does his diagnosis sound reasonable?
> > If it does sound fair, then what is involved in fixing it, given that
> while I've got the head off, I might as well prepare for unleaded fuel?
> Thanks
> Paul
> 74 TR6 PI
> Cape Town
Hi, Paul
>From what you say about #2 cylinder being cooler, makes me wonder if its
firing at all! Cracked valve seat, duff ignition or zero fuel supply are the
pointers. Have you done a compression test? It should be around 160-180psi
for the PI engine.
You haven't said anything about injector pipe *pulsing* as fuel goes down
it. If there's no pulse, it's likely the injector is blocked. A quickie way
(though dependent on crud content) is to pull the injector with the engine
running and flick the tip of it with your finger nail. If all you get from
it is no conical spray or just a dribble, then there's a block. However, the
key question is 'where is the block'? To exhaust all options, fit a new fuel
filter at the back end and use an airline to blow down the supply pipe to
the disconnected pipe on the metering unit. Suggest taking the metering unit
off and removing the gauze filter to #2 pipe on the MU. However, you're
probably aware that refitting the MU is pretty critical in ensuring its
timing isn't disturbed.
You don't say whether you've recently switched (by choice or necessity) to
unleaded fuel. If you have, its likely the fuel has attacked the seals in
the MU and they're breaking up. If so, no option but to take the MU and
injectors to an injection specialist and have the whole lot re-sealed. Hope
this helps
Cheers, Jonmac
1970 2500PI Saloon
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