REFLECTOR:Rough Rider
Fred Marconi
reflector@tvbf.org
Mon, 21 Jul 2003 10:01:32 -0400
Chuck:
Try wrapping the injector lines with an insulation material to reduce the
vapor lock issues. At idle place a fan on the air inlets to keep the engine
cool to see again if the problem is due to vapor lock. This should rule out
the vapor lock argument.
Fred
----- Original Message -----
From: "Chuck Jensen" <cjensen@dts9000.com>
To: <reflector@tvbf.org>
Sent: Saturday, July 19, 2003 10:24 AM
Subject: REFLECTOR:Rough Rider
> I have an engine issue that two mechanics have looked at...and that's all
> they've done. I wondered if anyone has ideas on avenues of
> investigation/solution. I'm running a 540 with mag/EI combo. The engine,
> particularly after a long flight (less so after starting cold), runs rough
> at ramp speed (1,000 rpm). Here are the symptoms with a hot engine after
> flight:
>
> As long as the booster pump is on, runs smooth as glass. VM-100 indicates
> 30 psi (from another post, is that way too high??) and approx. 4.0 gph
@1000
> rpm. If the booster pump is secured, fuel pressure drops to 28 psi, fuel
> flow shows 1.7 and engine bounces between 650-700 and just barely stays
> running. Turn the boost back on, and it immediately goes back to smooth
> operations with the first set of values. Turn the boost off, and it's
right
> back in the dumps.
>
> At cruise or high power operations, the boost pump on/off makes no
> difference in fuel pressure, fuel flow or smoothness of operations.
>
> One mechanic suggested that the idle speed needed to be increased. ??
> Seems he was missing the point. I'm intentionally setting it at 1,000 rpm
> with the booster, then engine goes in the toilet when the booster is cut.
>
> The second mechanic increased the richness setting which may have been too
> lean since I did not get a temporary rpm increase when cutting off the
> mixture, but the reliance on the booster pump did not change for smooth
ramp
> operations (especially when hot).
>
> Induction plenum has been checked thoroughly but that would seem to be
> unrelated to the observed symptoms.
>
> Questions: 1) are my fuel pressure values way out of line (earlier post
> talked about 5-6 psi)? 2) if my numbers are bogus, do I
> have a bad fuel pressure sensor or ground?
> 3) what do others run for fuel pressure/flow at 1,000 rpm on
> a 540?
> 4) is the main fuel pump going in the crapper? (its been
> this way for a long time with no further
> degradation/change)
> 5) is this type of poor low power performance characteristic
> of deterioration of the positive displacement type
> fuel pump?
> 6) is there a way to check the main fuel pump performance?
>
> I was in the camp that the main fuel pump is going downhill but I don't
> understand why, if it is putting out that much pressure, why the fuel flow
> should fall so much when the booster pump is secured.
>
> By all rights, these questions should be investigated and fixed by a good
> mechanic (which exempts me), but since that avenue has been unproductive,
I
> thought I'd check out the collective wisdom/experience of the
Reflectorites.
> Best idea wins an official Atta Boy award; redeemable wherever good ideas
> are sold.
>
> chuck
> N27GV
>
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