Mark,
If you've experienced the stumbling only during hot weather, I'd guess that
you've experienced "almost vapor lock". The symptoms don't sound to me
like fuel pump -- the 59 (IIRC) lb/hr Holley injectors required close to 20
psi and the Rochester 80 lb/hr only 12-13 psi. So pressure should not be
the problem and the pump should easily provide adequate volume --
especially at the low speeds you mentioned.
The whole world will give you corrective actions for vapor lock -- IF your
conditions make that likely.
Ken H.
> ...
Any chance you remember what the symptoms the 60 vs 80 pound injectors
> were? My coach had a Howell TBI installed on it when I purchased it, and I
> periodically get an engine stumble coupled with a check engine light that
> throws a lean run code... It seems to happen most after sustained running
> at a given throttle setting, and then some sort of major change... For
> example getting off of the highway after a sustained run, or getting on the
> highway after a sustained run on surface streets.
>
> The stumble goes away after a short period, and from what I understood
> there was not much to "tune" on the non-EBL Howells, other than the fuel
> pressure, so it's been on the back burner for some time...
>
> I did take the time to install a fuel pressure gauge, and I am not seeing
> any sort of drop in pressure when the stumbles occur... My next step was to
> install a wideband just to see where the setup had me running mixture-wise
> and go from there...
>
> Gonna go out and check the part number on my injectors shortly...
>
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
If you've experienced the stumbling only during hot weather, I'd guess that
you've experienced "almost vapor lock". The symptoms don't sound to me
like fuel pump -- the 59 (IIRC) lb/hr Holley injectors required close to 20
psi and the Rochester 80 lb/hr only 12-13 psi. So pressure should not be
the problem and the pump should easily provide adequate volume --
especially at the low speeds you mentioned.
The whole world will give you corrective actions for vapor lock -- IF your
conditions make that likely.
Ken H.
> ...
Any chance you remember what the symptoms the 60 vs 80 pound injectors
> were? My coach had a Howell TBI installed on it when I purchased it, and I
> periodically get an engine stumble coupled with a check engine light that
> throws a lean run code... It seems to happen most after sustained running
> at a given throttle setting, and then some sort of major change... For
> example getting off of the highway after a sustained run, or getting on the
> highway after a sustained run on surface streets.
>
> The stumble goes away after a short period, and from what I understood
> there was not much to "tune" on the non-EBL Howells, other than the fuel
> pressure, so it's been on the back burner for some time...
>
> I did take the time to install a fuel pressure gauge, and I am not seeing
> any sort of drop in pressure when the stumbles occur... My next step was to
> install a wideband just to see where the setup had me running mixture-wise
> and go from there...
>
> Gonna go out and check the part number on my injectors shortly...
>
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
