symptoms that lead to hot-wiring fuel pump?

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Blazer406

Mechanical Engineer
Joined
May 2, 2002
Messages
5,068
Hey guys.... just getting around to hot wiring my fuel pump.... it is a Walbro 307.... ordered a 340 over 2 months ago... still haven't got it :-(

I was going to wait to do the hot-wire when I installed the 340.....

I currently have a pretty much stock motor.... all car's mods listed in my sig....

Question.... What symptoms do you have if you "need" to hotwire your pump..... ie. "My car used to hesitate some during a blast.... and after I hotwired my pump...... it went away....."

I don't see anything in my DS logs to suggest I am starving for fuel.... but I get some periods of not pulling smoothly during a short blast..... like it pulls good for 3-4 seconds.... nice and smooth... and then hesitates ever so slightly..... for a second or two.... and goes back to pulling smoothly....???

I got to thinking that maybe the stock O2 sensor response was not fast enough to see this.... i.e. the DS log shows fine for O2 mV throughout the run... even though there was some hesitation.

I didn't notice any of this hesitation when I was down at 13 psi boost.... but now that I am running 23+ ... it is there..... just have never figured out what it was.......

Any ideas?
 
misfire?

Hi,
Well, I used to get horrible misfire before going to the Walbro 340, which I installed with a racetronix hotwire kit,but it was obvious that the pump was at fault because o2 voltage plummeted under load.I don't run anything like your boost levels, and wonder if knock retard could be a possible culprit.What is the knock counter saying? Besides that,maybe injectors aren't up to the job, or the chip isn't right.Other possibilities include Tps and Maf.Even with our limited scanner data and speed, something should show you the right path. Good luck!
 
83ttypecooled said:
Hi,
Well, I used to get horrible misfire before going to the Walbro 340, which I installed with a racetronix hotwire kit,but it was obvious that the pump was at fault because o2 voltage plummeted under load.I don't run anything like your boost levels, and wonder if knock retard could be a possible culprit.What is the knock counter saying? Besides that,maybe injectors aren't up to the job, or the chip isn't right.Other possibilities include Tps and Maf.Even with our limited scanner data and speed, something should show you the right path. Good luck!


I am running DS... it updates up to 18 times per second..... I don't have any knock retard..... occasionally I get some knock counts right when I stab it... but any of the hesitation I have.... is usually later in the blast.... like midway through 3rd....

As far as injectors... they are 60# Motrons.... defiantely up to the task of mid 10's..... currently my car is probably capable of low to mid 12's.... @ 23 psi.... maybe a little quicker depending on the 60' time... need to take it to a quarter mile track when I get through upgrading the rear suspension...and tires. The TPS and MAF stays pegged (the TT chip keeps the MAF pegged....when at WOT anyway) DS shows no problems with the TPS.... .44 volts idle.... about 4.55 volts at WOT.....
 
misfire

Hi,
You have a tough one here, and I'm out of my sphere of experience, with that high boost you are running. Do you run 23 psi on the steet? Try this: cut the boost back in 2 psi increments until the problem stops. Find your functional level, then run the car at the strip and see what happens. Oh, and what plugs are you running? i hear that closing the plug gap to .030 or so can help, but again don't have personal experience. Sorry that my my box of silver bullets is so small, good luck!
 
Add some more timing, its probably rich if you dont get alot of knock.
Pull a spark plug, what color is it?
try adding one degree of timing and see what it does, nosing over usually is rich or lean on the top end of each gear. Your DS is showing no knock, so it may be rich.
What is your egt at the top of 3rd gear?
BW
 
By the way, i run 28° in first and second and 25° in third with 30# injectors with a SMC kit running a single -15 hago? jet and 92 octane with the pump set at 6... boost at 20psi..... 3850#s
BW
 
i think you answered your own question in regards to hesitation went away you might get the pressure without hotwire but you will lose volume at high boost levels you might have 60 to 70# but your o2's will drop i think when you goto a 340 all you have to do is install and plug it in if you hotwire now
 
lpaulabbott said:
i think you answered your own question in regards to hesitation went away you might get the pressure without hotwire but you will lose volume at high boost levels you might have 60 to 70# but your o2's will drop i think when you goto a 340 all you have to do is install and plug it in if you hotwire now


Well... O2's never go below 800.... most of the time they are in the low 800's. Even during the hesitation....they aren't showing lean. That is why I was asking if the narrow-band sensor has a slow response or not....I think that if it does have a slow response... that maybe my pump is pulsating...trying to keep up and during the pulses...the pressure is dropping enough for me to feel it.... but not for a long enough time to show up on the O2 voltage?

Quick6'n'-K.C. said:
Add some more timing, its probably rich if you dont get alot of knock.
Pull a spark plug, what color is it?
try adding one degree of timing and see what it does, nosing over usually is rich or lean on the top end of each gear. Your DS is showing no knock, so it may be rich.
What is your egt at the top of 3rd gear?
BW

I need to pull the plugs....and check. Plugs are R43's gapped around .030" Might need to go to R42's ....

I will definately try and bump timing up.

I also intend to lean it out some. I have pretty much leaned it out as much as I can with the chip.... next step is to drop fuel pressure a lb or two and try it. I can't remember where I set my fuel pressure... it was either 43 or something real close with the line off (whatever psi the extender instructions said to set it at).... I have not fiddled with it since I installed my extender chip a couple months ago.... when I got the used TT chip in.... I didn't change the FP.

I need an EGT. I have an old VDO one... but it is broken... (reads like 300 deg not hooked up). I really want one I can log. I really want a datalogger for boost... FP....TPS....EGT...ect.... but don't know how I am going to accomplish this on a budget....

I need to go borrow my brother-in-laws Innovate Wideband setup and put it in my car.... I can datalog with it... his has the RPM module... so I could log like 5 other things too. Maybe I will get it before I go to the track again.....

Quick6'n'-K.C. said:
By the way, i run 28° in first and second and 25° in third with 30# injectors with a SMC kit running a single -15 hago? jet and 92 octane with the pump set at 6... boost at 20psi..... 3850#s
BW

I really think the timing might help as well... I am only running 23 deg in 1st and 2nd and 20 deg in 3rd. I have not fiddled with the alky settings on my Razor's kit... except for the blue knob..... which only changes the overall amount of alky coming out..... usually it stays around 50% (half way up). Gas is 93 pump gas. Alky is 100% methanol. I think my chip will let me go -1 to +4 on the base timings in the chip (23/20)..... so I guess.... theoretically could go as high as (27/24) as long as there was no knock....
 
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