Technical Fuel Pump Question
#1
Technical Fuel Pump Question
Calling out the big brains. Fuel pressure should be around 39 lbs at idle (no vacumn) mine is 25. Problem appears to be intermittent. Relaced fuel pumps( two sets of hi flow Walbros), no help. Now on my second adjustable fuel regulator (CPR and Aeromotive). 25 pounds no matter the adjustment on on the regulator. 25 pounds when return line is blocked as well. Does anyone know what the low and high voltages should be to our pumps, as our pumps are two stage? Any other ideas on solution to this problem?
99L
99L
#5
fuel pressure problem
I have same 25 psi problem. Checked filter -ok. Mods are (2) Walbro gss340 (255i) pumps, super fmu, 50lb/hr injectors. Contacted Walbro - lightning replacement pumps gss310 drew 4.5amps@40psig and the gss340&gss342 drew 7amps@40psig.
I measured 12.7 amps@40psig with the gss340. 1 pump 40psi 2 pumps@25psig. Measured draw 6.5amps@40psig each. Switching to gss310.
Some trucks get away with 255's ours wont. It basically is to much current draw before the highlow relay clicks on. If you want to see if your truck has the same problem short #30 to #87 on your high/low relay. If it fixes your problem I suggest making the same change.
Good luck!!!!
Walbro #989-872-2131
nist@dukesinc.com
I measured 12.7 amps@40psig with the gss340. 1 pump 40psi 2 pumps@25psig. Measured draw 6.5amps@40psig each. Switching to gss310.
Some trucks get away with 255's ours wont. It basically is to much current draw before the highlow relay clicks on. If you want to see if your truck has the same problem short #30 to #87 on your high/low relay. If it fixes your problem I suggest making the same change.
Good luck!!!!
Walbro #989-872-2131
nist@dukesinc.com
#6
I'm working on this issue. I spoke to the performance engineer at Walbro today, he is stumped. Fuel pressure is controlled by the regulator, so he can't see why LARGER pumps would cause a drop in pressure. The only thing he said, was that maybe the low sdie voltage is too low. Steve measured his low side voltage and only saw 5volts. Walbro said the pumps don't work well under 7 volts. However, I've sold hundreds of these 255 kits over the past few years, and not one truck ever had a problem, until recent. Five volts seems a bit low to me. I'm wondering if some trucks have higher resistance on the low side ground resistor wire than others, dropping the voltage too low to properly operate the 255s. I'll keep evereyone posted on what we find. BTW, the GSS340 is not the correct pump for us, you need the GSS342s.
#7
Trending Topics
#8
Originally posted by LightningTuner
I'm working on this issue. I spoke to the performance engineer at Walbro today, he is stumped. Fuel pressure is controlled by the regulator, so he can't see why LARGER pumps would cause a drop in pressure. The only thing he said, was that maybe the low sdie voltage is too low. Steve measured his low side voltage and only saw 5volts. Walbro said the pumps don't work well under 7 volts. However, I've sold hundreds of these 255 kits over the past few years, and not one truck ever had a problem, until recent. Five volts seems a bit low to me. I'm wondering if some trucks have higher resistance on the low side ground resistor wire than others, dropping the voltage too low to properly operate the 255s. I'll keep evereyone posted on what we find. BTW, the GSS340 is not the correct pump for us, you need the GSS342s.
I'm working on this issue. I spoke to the performance engineer at Walbro today, he is stumped. Fuel pressure is controlled by the regulator, so he can't see why LARGER pumps would cause a drop in pressure. The only thing he said, was that maybe the low sdie voltage is too low. Steve measured his low side voltage and only saw 5volts. Walbro said the pumps don't work well under 7 volts. However, I've sold hundreds of these 255 kits over the past few years, and not one truck ever had a problem, until recent. Five volts seems a bit low to me. I'm wondering if some trucks have higher resistance on the low side ground resistor wire than others, dropping the voltage too low to properly operate the 255s. I'll keep evereyone posted on what we find. BTW, the GSS340 is not the correct pump for us, you need the GSS342s.
Any updates, I have the same issue. Just installed 2 225s.
Mark
#9
Originally posted by HIHOAG
Sal,
Any updates, I have the same issue. Just installed 2 225s.
Mark
Sal,
Any updates, I have the same issue. Just installed 2 225s.
Mark
The solution? Buy a second fuel pump dropping resistor, and wire it in in parallel with the original. That changes the stepped voltage from 7 volts to about 9 volts, and then the 255s move enough fuel to make it all happy again.
Hope this helps.