Low fuel pres + turn pump ?

[WJune]

Been working on the Gray Dog last three days getting ready for my annual 5 day trek to Iola. As mentioned in another thread, truck runs good empty although lacks low end torque, I think ? 3:55 gears an under 35 in 4th she jerks.

Valves in speck, injectors just checked, replaced #6. Almost impossible to make smoke, maybe a little in 3rd WOT. Virgin pump, with top smoke screw turned in with maybe 3 threads showing. Filters changed. Additives used.

Finaly put fuel pres gauge on after filter 2-3 psi on 60 # gauge ( was in a hurry ). Thats new after market pump, tried spare used pump 0#s!

Tried couple diff electrics pre mech. pump, same reading. Tested elect off truck 10#'s. Put best pump back on, road test, seems peppy with foot in it, although low end weak. Chuggs under 35 in 4th.

Also made pump wrench, finaly got pump to barely turn 1/16 th. Turn down seemed retarded idle rough an smoke. Turn up, little or no diff from stock setting. Seems rattely anywhere its set. Wether KSB wire is on or off, no diff. Solenoid ok, tried 3 diff ones an it gets warm.

Oh, the full fuel screw is banded like a Pheasant, plus soldered or something ! Need to pull a trailer weds afternoon, lucky no hills ! thanks for listening. WJ

 

[dpuckett]

35mph in 4th is around 12-1300rpm, IIRC. (well under 1500). Peak torque is rated for around 1700rpm. So, it is no wonder with a stock truck, you have no pep at 35in 4th. You should see a pick up in speed and power around 40-42mph, with good power til about 65-70ish, where it will reach the defuel point. Stock trucks never take off and just run like a scalded cat. Tampered pumps on the other hand... ... .



Lack of smoke is not a bad thing- it means the engine is getting enough air to burn all the fuel completely. Makes for good EGTs and MPGs. At least better than leaving a trail of smoke everywhere.



I'd also recommend a gauge with a lower max pressure. I have read that gauges are accurate as a percentage of the max. So, on a 60psi gauge, accurate to +/- 5% (I know, a gauge with that accuracy is useless, but it makes my point), that is +/- 3psi; on a 15psi gauge, it is only +/-. 75psi. try to find a 10-15psi gauge, and see what you get. My Airtex pump makes about 7psi at light loads, and I can PULL it down to about 3psi with 34psi boost, and 1050EGT (60/12 turbo helps there Oo. ) Digital gauges are about useless, IMO. I used one on my 91 that said I had 0 pressure. I hooked my boost gauge to the same fitting, and got 6psi. This was the super-super gauge that my g/f's shop uses for their diagnostics. Makes me wonder how many fuel pumps have been replaced that actualy didnt need it?



Daniel

 

[WJune]

Thanks Daniel, plan to find a better gauge at Iola if I ever get there. Put the inj pump back to stock today as didn't like the sound, and empty the power seemed to come at even higher rpm's. I don't expect to mash on it at 35 mph in 4th, just want to do the speed limit as I go into town. Hate reving along in 3rd with a stock eng. Back in the day with a cammed up 327 in my 57 chev it was fun.

Even my 300 6 in heavy stepvan will do 25 in 4, no prob. My other CTD's are down with sick trans so I have nothing to compare with. Last year I rode in a friends similiar 1st gen an was amazed that his trans was quiet, an as a test he lugged it I beleive down to 25 in 5th !

Anyone with a stock truck care to comment on city driving.