My Holley Red starts at 7psi when it's cold, then as it warms up drops down to 3psi, and sometimes bounces between 3 and 4 psi. Anyone else ever had this problem? I think it's causing my engine to run too lean when the EGR comes on. It runs fine at WOT though. Voltage stays between 14.22 and 14.12, and I've only checked the current when it's hot and it was at 1.23A.

 

I forgot I had an illustration of this effect.

Some more info: When pic was taken, the car was on a 45-degree downward slope and the fuel would go toward the front of the car. Also the fuel pump is mounted in the engine bay next to the coolant reservoir.

 

1 Problem may be the position of the pump itself. Generally Its alot better to mount them as close to the fuel tank as possible.
Its better because most electric pumps are alot better at pumping then they are at sucking fuel. When its mounted in the engine compartment the fuel is only gravity feed up to there so its a low pressure at the pump making it harder for the pump to push at full psi.

 

I figured someone might say that, but would it still make a difference since it's on a 45-degree incline? Also it starts out at 7psi and takes a few minutes to get down to 3psi, so the placement of the pump and where the fuel is stays pretty much constant while the pressure changes.

 

how do you have it plumbed? seems like its sucking air or maybe has a restriction.

 

just had a flashback looking at that filter, it'll clog real easy. i had one one my car when it had a mechanical pump. stranded me twice. that little screen , it made me walk afew times

 

I used the stock aluminum line up until it turned to rubber, then replaced that rubber hose with a shorter one that goes onto a 3/8" hose barb into the fuel pump. From the fuel pump it goes into a -6 AN fitting into Earl's stainless braided hose with an auto-fit end, to the filter, which has 5/16" barbs on the end, then out to another stainless hose, then into the carburetor with another auto-fit hose and q-jet adapter.

When everything is cold or just warm and I start the car, the filter is completely full with no air going through, and running at 7 psi.

Also I might add that when I ran 15.3@89 in the 1/4 the car sounded completely smooth, and everything was pretty much cool or just warm.

 

was your car fuel injected originally? if it was maybe the sock in the tank is plugged. thats how mine acted with the filter plugged. if i let it set the fuel would fill up the system and start the car, then it would die. and like that other post electrics are made to push not suck, it could be the pump getting hot. have you checked the volts at the pump when this happens or are talking about your gauge reading? i think there is aspring that can be replaced in the pump as a kit, that could be apossibility

 

What would be the correlation between placement and it getting hot?

It's always had the q-jet, it originally had only a mechanical pump. Those are voltages listed above, it never goes above 7 psi. The only symptom I have is that my engine pings and runs lean under the same conditions that the EGR is supposed to come on. This fuel pump thing is something I noticed, and I'm wondering whether it could be the cause of that, and whether or not my fuel pump is defective.

 

if the pump is getting hot it could be low voltage to it, a restriction or something bad going on. heat isn't good for electric stuff , your resistance goes up drawing more current more heat and so on. the egr valve puts exhaust into the intake charge for emissions that will lean it out. depending where you live you could remove it.you could fatten up your jetting, retard the timing

 

You really need to move the fuel pump back near the tank.It should be no further than a foot or two max from the tank and below the tank to let gravity feed the fuel to the pump.Mount it behind the driver side rear seat.The pump is trying to suck fuel from the tank..in your case about 10 feet away which it is not designed to do..meant to push.The pump working that hard to move the fuel from so far away will cause it to heat up/overheat too much.Don't forget the fuel acts as a coolant.The fuel when it finally gets to the pump is overheating from the great distance and causing the pinging and lean condition...close to vapor lock.And if you are parked on an incline the fuel will have to gravity flow to the filter which can be a problem if the filter is higher than the tank..car facing uphill?Fuel will want to flow away from filter..hence the empty filter.But you say you were facing the other way.Is your filter before or after the pump?

 

Just my 2 cents about those frickin glass filters-get rid of it and buy the -yes ugly-fram metal or plastic contained paper element filters. I got the 110gpm mechanical Holley and when I had the glass filter like that one, somehow, the fuel pressure would bleed off immediately and the filter would be empty, I bought the plastic Fram unit 3/8" in & out and the thing is still full the next day, not only that the glass ones are very restrictive with the orficies that the actual fuel flows through, they are prettier, but after much hounding from alot of people that had them and switched over I did the same, didn't notice any E.T. difference, but I like knowing that when I start the car the fuel is right there ready to go. And yes like everybody said mount the pump as close to the tank as possible.

 

That makes more sense. Also, the filter's after the pump.

Craig, for future reference current will actually decrease as resistance increases according to the equation R=V/I.

I'll look into moving the pump to the back and moving the filter before the pump to see if that helps, I was planning to re-design my fuel system in the near future anyways. I'll look at some other filters also. I don't care about the looks of the filter, I just liked that I could see what was going through it. Thanks for the input guys.

 

Ohms law is to find the resistance of an object/substance when a nominal voltage is given by dividing it by the current allowed to pass through it. Its not meant to be used for this in the way you stated.
What actaully happens, is as the pump's resistance "R" goes up, the current "I" needed to maintain the same voltage "V" will go up, since teh voltage of the battery does not fluctuate that much.
Thats ohms law in this form, IR=V. So if the voltage of the battery stays about the same, the resistance is high/goes up, the current will need to be higher then normal, but its not... so the voltage on the other side of the resistance (oposite of the battery) will be lower, and the pump will not function to its full potential. Sorry if i make little sense, but its the easiest way i can explain it.
If you dont beleive me, u can go to radio shack grab a couple resistors, a 9v battery, and a motor meant to be run with a 9v battery... run it with just the motor, then run it with the motor in series with the resistors. Or even just take a voltmeter to some batteries with or with out resitance in series, both current and the voltage will drop.
Either way, dont mean to rag on you, good luck hope you figure it out.

 

hey now if we want to get into ohms law , i've been an industrial electrician for 22 years now. theories aside when the motors get hot the current goes up and that is checking with a clamp- on ammeter and a temp probe. oh well didn't mean to rant

 

Well, from what it looks like you have more knowlege on the subject, so tell me if im wrong when i say one of 3 things can happen if a motor increases in resistance.
1. It draws more current
2. Its voltage drops
3. Both of the above
From what I know thats what happens.

 

I said that based on the new measurements I made on Sunday. I measured the voltage at outside temp and it came out to be 14.62V and 2.02A. When it dropped down to 3psi I measured it again and it came out to 14.22V and 1.23A. If you plug those into the equation you'll find that the resistance of something increased. Yes, it is true that the voltage drop would be after the pump if its resistance went up, and that the voltage before it should be constant. That was my mistake, I apologize. So realizing that led me to think that maybe something in the circuit before it was increasing in resistance, which might give those results. Today when I got home i checked the voltage again and it was about 14.21V and the current was about 1.22A. I pulled the inline fuse right before the pump and ran the ammeter through the battery, and still got 1.22A. I checked the voltage coming from the relay with the fuel pump disconnected and it came out to be 14.21V, so I measured the voltage across the battery and alternator and they came out to be the same also. All measurements were taken before the fuel pump by the way. If someone thinks it would be useful info I could take measurements after the pump also.

Didn't mean to insult anybody or anything from that statement.

Also nbn792, are you saying that as R increases when V is constant then I increases according to IR=V? Sorry if I misunderstood.

 

As far as i know if the resistance goes up..... it will draw more current to keep the same voltage in the motors case, but a true resistor will limit the current allowed to pass and very slightly lower the voltage. However drawing current is different then the current allowed to pass through.. which is more of what ohms law is concerning. A motor will draw current, while a resistor or a resistance in the circut(including a higher then normal internal one in the motor) should lower currrent allowed to pass. But if you really have a question ask craig as he has more experience then me, im not an electrician, i just build tube guitar amplifiers as a money making hobby. However i woudnt even bother thinking about it before you move that fuel pump closer to your tank. good luck. You could try measureing the current way before the motor to see if there is soemthing in the circut causing the resistance. It could be that not enough fuel is reaching the pump and that the current draw is lower because the motor is not being strained as much, therefor not needing the same amount of power to run it???