With the tps voltage,if the voltage at idle is correct(i'm getting 0.46 volts),should that mean that the wot voltage will be correct?,as i only get 1.3 volts at wot.Also with the mcs,should the clicking be loud all the time,(a strange question i know)because on my carb it is loud then quiet,almost to the point of not being able to hear it.This is without the engine running.

Alicat.

 

In all likelyhood the TPS is shot. If it's reasonably close at idle then it should be reasonably close at WOT. There's not much adjustability in the linkage. Certainly not enough that it would make 3+ Volts of difference.

 

Damon,thanks for the reply.This is on a holley rebuilt unit from summit that i've only just recieved.Surely they would put a new tps in when they rebuilt the qjet.I will be pissed if they didnt.Also any ideas on the mcs noise.
Maybe it does'nt mean anything.

 

Check the voltage at all 3 wires of the TPS.... one should be at 5V all the time, one should be at ground all the time, and one should vary smoothly from about .5V to about 4V as you open the throttle.

If you don't have the right 5V there to begin with, you can change the TPS every day, and twice on Sundays, and still NEVER get the right voltage at WOT.

 

Well i just went and checked and i got a different result.5.03 v at term A.
.56 v at idle ranging up to 3.9 v at WOT,this was at term b.
1.0 mv at term c,ground.So this now seems correct.The only difference between the two tests was the engine was hot on the first result,and cooled down on the second test,although not cold.does engine temp usually have this effect?.
I'll try it again in the morning when its cold.

Alicat.

 

Hi alicat, Is it possible your first readings weren't making good connection? 4V sounds better. About your MCS, it usually will shutoff after a minute if the engine isn't running.

 

HiTrumps,I checked the tps voltages this morning,and it seems ok still.One thing i noticed was that the throttle linkage is holding the tps plunger down slightly,resulting in a voltage of 0.70 volts at idle,but when i pull the linkage right back,the idle voltage is in spec.Still 3.9volts at wot though so it's ok.In regards
to the MCS the dwell checks out ok,just that the clicking is loud then quiet,whereas on the old carb,the clicking volume was always audible.As i said if the dwell is ok the volume question is probaly meaningless.

Alicat.



P:S,I think the reason for the errant tps reading,was a bad ground.

 

Keep in mind that the MCS is submerged in the fuel well of the carb. Varying levels of fuel could change the tone or volume of the clicking. If it starts out loud then quietens down after a few seconds, your bowl could be empty and getting re-filled by the pusher pump in the tank, even with the engine off. You could easily test this by crimping the rubber fuel line to the mechanical pump and seeing if the volume or tone changes while its held crimped.

Not sure that the little pump in the rear has enough pressure to push fuel past the needle/seat assembly though. Bottom line: I wouldn't worry about it.

In case someone else looks here with a similar issue on the TPS; I experienced this exact problem with one once (0.40 volt to about 1.5 volt) and it was caused by the TPS spring weakening and allowing the TPS to move down in the bore as the throttle was depressed. Likely caused by the old TPS getting gummed up and adding resistance to the plunger.