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MagnaFuel Pump Issue(s)????


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Fuel pump is a Magnafuel 750 ProTuner(electric), dual relays, pre-filter, post filter.

Car started right up, puttered down driveway, turn on street....dies in middle of street.

Cranks, pump makes pumping sounds...0 psi at gauge and no start, tow back to house(not fun)

Change two relays in engine compartment because of a strange reading....pump primes with

key, just no psi. 12.5-12.36v at battery, 11.7 at rear relays and pump. Call Magnafuel

and he had a few things to check and mentioned if rear relays(3-4 yrs old) are failing that they might cause the issue.

Now the funny part. When out and actually tried to start the car(did not bother since

there was no psi showing(after eng. compartment relay change)....fired right up ran it for a bit, shut-off and it restarted(Thurs.)

Went out Sun. am for a cruise, starts right up, puttered down drive, make turn, F-in died

in same spot. Won't restart again(no psi)...push back to garage.

Still get 11.7v at rear relays, 11.7 at pump, but if you crank eng. it drops to 10.36(at

pump).

Tech line was very specific about needing 12.5-14 at pump for proper operation. If you

jump from battery to pump(12.4v), you get 40-42 psi at gauge in less than 10 sec. Local

parts store ordered the wrong relays for pump, so changing that will have to wait till next

week. I was always under the impression that relays worked or don't, is it possible that

these are still working(they click with key), just not letting enough power to run pump

properly?

All heavy gauge wire, soldered, nothing corroded or loose.

Very frustrating.

 

B&G

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Undersized cheap relays burn up contacts, induce voltage drop, cause problems.

 

Relays were never "work or don't" -- your voltage readings told you that, your jumper test directly to the pump from the battery told you that, you just discounted it in both instances for some reason.

 

/Obi Wan Haunting Voice/

"Blackdog NY, trust your instruments, they show lack of The Electromotive Force!"

Edited by Tony D
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Not undersized, (2)40/30A, which is manufacture's requirement. Yes, they are original, not that old and Tyco

brand. No burning, heat, discoloring or corrosion.

Ordered replacements(and 2 spares from Summit last nite).

I said I 'thought' relays worked or didn't...hence the question(s) posted.

Always appreciate responses, even one that is not that useful.....should I duck for incoming 'sparkplug'.

 

B&G

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Not undersized, (2)40/30A, which is manufacture's requirement. Yes, they are original, not that old and Tyco

brand. No burning, heat, discoloring or corrosion.

Ordered replacements(and 2 spares from Summit last nite).

I said I 'thought' relays worked or didn't...hence the question(s) posted.

Always appreciate responses, even one that is not that useful.....should I duck for incoming 'sparkplug'.

 

B&G

It's only "not useful" if you choose to ignore it.

 

The relay rating of 40/30 just means that it _probably_ won't start on fire or melt down at those current levels.  It says nothing about the amount of voltage drop you will see.  

 

Actually, that's not completely true - it does in fact say that you will have a large enough voltage drop that the resulting power dissipation (power dissipated = voltage drop X current flow) will be high enough to melt the relay at somewhere above 30A.  If you require low voltage drop in addition to a current spec, you should get a relay that is rated for a MUCH greater current than you will be flowing through it.  For instance if your pump will require 20A and you can't live with low voltage, get a relay rated for 80A or higher.

 

12.5V _minimum_ is ridiculously high for an automotive pump, BTW.  All OEM stuff is required to work down to at most 10V.  Are they really saying that the pump shouldn't be expected to prime and work at all at that voltage, or are they just saying that it won't meet it's flow specs?

Edited by TimZ
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Cranks, pump makes pumping sounds...0 psi at gauge and no start, tow back to house(not fun)

Change two relays in engine compartment because of a strange reading....pump primes with

key, just no psi. 12.5-12.36v at battery, 11.7 at rear relays and pump

It doesn't look like an electrical problem.

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Cranks, pump makes pumping sounds...0 psi at gauge and

 

pump primes with

key, just no psi. 12.5-12.36v at battery, 11.7 at rear relays and pump. Call Magnafuel

 

Still get 11.7v at rear relays, 11.7 at pump, but if you crank eng. it drops to 10.36(at

pump).

Tech line was very specific about needing 12.5-14 at pump for proper operation. If you

jump from battery to pump(12.4v), you get 40-42 psi at gauge in less than 10 sec. 

Just to focus a little more, the extra juice when running directly from the battery is probably over-powering the blockage.  It shouldn't take 10 seconds to get to 42 psi.  You might be overheating the pump due to low flow from a blockage or a too-small inlet filter.  The key though, is that you hear the pump spinning and you're not getting pressure.

 

There's something odd about the specs on that pump though,  The Summit Racing site says it draws 14 amps at 45 psi.  That seems like a lot of amps.

 

Anyway, try it without the pre-filter and see what happens.

 

http://www.summitracing.com/search/product-line/magnafuel-protuner-750-series-in-line-fuel-pumps

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I did not ignore anything, Tony really did not answer any of my questions. He might have, in his own Mr. Miyagi

way??

As far as the voltage needed, don't blame me....That is what the MANUFACTUER REQUIRES....if you disagree I am not going to argue about it. Tech guy said having the 11.7 at pump was low, but should not prevent psi production

until running conditions. The relays that are in the car are the ones that came with the fuel system, all the same stuff. Replacements are from Magnafuel as well. I am by no means a electrical person, but putting a higher than

spec relay in seems the same as putting a higher amp fuse in your home breaker panel because it keeps tripping.

Won't it let more volts than needed to pump(or your home's outlet) which will only lead to a visit from your local

FD.

If the fuel line was blocked, why would it produce 40-42 psi when jumped from battery? Also started right up,

idled fine and just died. I guess something maybe floating around in filter and getting clogged and then without pressure it floats around again. Seems less likely that relay issue, but when my an wrenches arrive I will clean/check the filters.

 

B&G

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Btw, the particular pre-filter, pump(750 protuner) and after filter is rated to handle well in excess of 1000hp.

Not you little pump you see in a 100hp Honda.

Ya, it might draw some power......

And the 10 sec. time was 'about 10 sec.' I was under the car holding the alligator clips on the pump and I had to get out from there to see the gauge.

And, no the pump did not get hot when cranking...had my hand on it...felt like cold alu.

Inlet filter is from Magnafuel, came with pump.

Remember I drove this car home 90 miles 3 days before it died(the first time). No bogging or misfires that would indicate filter blockage.

 

B&G

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I did not ignore anything, Tony really did not answer any of my questions. He might have, in his own Mr. Miyagi

way??

As far as the voltage needed, don't blame me....That is what the MANUFACTUER REQUIRES....if you disagree I am not going to argue about it. Tech guy said having the 11.7 at pump was low, but should not prevent psi production

until running conditions. The relays that are in the car are the ones that came with the fuel system, all the same stuff. Replacements are from Magnafuel as well. I am by no means a electrical person, but putting a higher than

spec relay in seems the same as putting a higher amp fuse in your home breaker panel because it keeps tripping.

Won't it let more volts than needed to pump(or your home's outlet) which will only lead to a visit from your local

FD.

If the fuel line was blocked, why would it produce 40-42 psi when jumped from battery? Also started right up,

idled fine and just died. I guess something maybe floating around in filter and getting clogged and then without pressure it floats around again. Seems less likely that relay issue, but when my an wrenches arrive I will clean/check the filters.

 

B&G

 

This paragraph:

 

 

Still get 11.7v at rear relays, 11.7 at pump, but if you crank eng. it drops to 10.36(at

pump).

Tech line was very specific about needing 12.5-14 at pump for proper operation. If you

jump from battery to pump(12.4v), you get 40-42 psi at gauge in less than 10 sec. Local

parts store ordered the wrong relays for pump, so changing that will have to wait till next

week. I was always under the impression that relays worked or don't, is it possible that

these are still working(they click with key), just not letting enough power to run pump

properly?

 

...is what Tony and I were responding to.  Specifically the answer to your question in the last line was "yes".  Tony spelled out the reasons for this, but left it to the student to draw the conclusion.

 

However, my mentioning that the 12.5V minimum was a ridiculously high requirement was meant to get at what they really meant by that - it does not make sense that the pump would not be expected to prime reliably at 11.7V, which is what you indicated that you were told in the above quote.  It does however, make some amount to sense that MagnaFuel would not guarantee meeting their specified flow at the lower voltages and/or that continuous use at lower voltages could cause reliability issues.

 

This was why I expanded on the notion that if you require a low voltage drop across your relay to your pump, then you don't want to be operating anywhere near it's max current rating.  This is NOT the same thing as putting in a larger fuse to keep it from blowing.  In fact it's the exact opposite.  Higher rated relays use larger contacts to get that rating, and will have a lower voltage drop at any specific current level than a lower rated relay.  You should never, under any circumstances, use a relay as a fuse.

 

BTW, a similar rule applies for fuses - ever wonder what the difference is between a "mini" and a larger "maxi" or "mega" fuse of the same rating?  Voltage drop is lower for the physically larger fuses, especially when you near the fuse's current rating.

 

All this said, I tend to agree that low voltage might not be your primary problem.  As others noted, it could be due to a restriction in the fuel lines.  I'm also suspicious of the feed line, though - can you give some more detail on how the fuel gets from the tank to the pump?  Reason I'm asking is that these type of pumps are fairly sensitive to cavitation, which can happen if you have too restrictive a feed line and/or if you have a vacuum in the tank because it isn't properly vented, and/or if your fuel temperature gets too hot in the tank.  Basically the pump will run fine for a while and progressively get worse until it can't make pressure any more.

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Don't take this the wrong way, I asked questions to get answers and maybe help somebody else with similar issues.

If Tony's answer was a simple 'yes' to my relay question....just say so. It would be soooooooooo much easier.

I will be using the magnafuel relays because they had worked just fine for 3+ yrs. and they don't offer any options(probable

for a reason).

From what I remember reading, they want that voltage for their pump to work as advertised. It had something to do with low

voltage causing the pump to draw higher amps. and possible damage. Don't quote me on that, my memory is not the greatest.

I believe it is gravity fed from a internal sump in tank. Not positive. It is a external unit with a pre-filter and post

filter. Has a fuel 'cooler' on return line. -10 or -12 lines. The tank is a stock looking exterior with custom baffles and

sump designed specifically for high hp efi's with power adders. Not sure on the vent, it is vented. This is not a 'thrown

together' fuel system. Previous owner had two other boosted power plants. They were changed for upgrades to car.

If I had a heat issue in the tank in the elapsed time from start-up to pushing back to garage, there is something major wrong.

Car was in closed garage, am temp was not above 65 and cruise lasted 5mins.

If you have any interest, the Magnafuel web page is small, but I might have some info on there you might understand better

than me.

 

Thanks again.

 

B&G

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Remember I drove this car home 90 miles 3 days before it died(the first time). No bogging or misfires that would indicate filter blockage.

 

Can't remember something that wasn't mentioned.  Your first post sounded like you just put a new system together, with old relays, and had problems.  If it's a new problem on an old system that used to work, that's a whole different thought process.

 

So, is everything 3-4 years old, and the problem is new, just out of nowhere?  Or are there new parts, and a new problem?  Did the relays you changed have any effect?  Correlate the changes and a cause-effect relationship might pop out.

 

Good luck.  Don't get side-tracked.

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Just got car, changed nothing, worked like a top for original owner.

I changed the factory relays, will be changing Mangafuel one when they arrive.

See previous posts for starting-dieing-pushing process.

 

Got to get to work....

 

B&G

...so the pump has been in the car and running like a top for years, months, weeks?

 

Does the tank's custom sump have an outlet fuel line barb like the stock tank, or is it an AN fitting?  What size?

What size is the hose from the tank to the pre-filter?

How is the return line plumbed into the tank?  Does it go into the custom sump. or somewhere else?

 

The cavitation issue that I mentioned can be a process of the pump slowly destroying itself for a period of weeks or months.  If it has been run in the past with any combination of the three issues I mentioned (inlet restriction, tank vacuum, hot fuel) that was bad enough to cavitate the pump, then the damage could already be done, and could have already been degraded when you bought the car.  The symptoms start with maybe you are driving around for a few hours and after a while the pump starts sounding funny, then it's max pumping capability goes way down (dangerous because it works fine until you run boost and then you get low fuel pressure), or maybe it just craps out.  Let it sit for a half hour or so and then it starts up again. Next day it seems fine, but the more often you take it out, the quicker those symptoms reappear, until at some point it just won't prime anymore.   I'm trying to discern whether or not this is likely to be your problem.

 

The fuel cooler on the return line could have been from an effort to address such a problem, btw.  Can you give any details on this?  What kind of cooler?  How big? Where is it mounted?

 

Do you have pictures?

Edited by TimZ
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In reverse....fuel cooler looks like one of those power steering coolers, about 1'Lx3"dia., alu. construction with

ribs that run the length. Mounted to floor just about under PS seat. Same -10 line. Its blue.

According to the original owner, he has never had fuel issues beside a relay(factory)replacement a few yrs. ago.

He seems honestly surprised that I am having problems. He does not strike me as someone who sold a car with known issues.

It is strange that the car ran so well on my way home, and for that matter around the guy's house(test drive) and it decides to crap out three days later 5 mins. after starting.

It looks like the return line enters the tank above the outlet(to pump). Now I know that is bad to have 'hot' return gas mix

with out going fuel. Just not sure what it looks like inside the tank. They might(and probable are) separated. Inlet to pre

filter is the largest line I can see -12? Others seem to be -10.

Pump really does not sound 'bad'. Is the cavitation problem like putting your hand over the end of a leaf blower...if you know what that sounds like. Engine is running, just no air is leaving...a higher pitch sound.

I kinda remember reading that cavitation will make the pump run hot, draw higher amps and vicious cycle to pump failure. That

being said, I have no evidence of things getting hot...wires/connections.

Think the magnafuel system has been in the car for 3 yrs.

Relays will be here Tues/Weds. that and a filter check/clean are next on my bucket list.

Sorry no pictures, yet.

 

Thanks,

B&G

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Well, she started again this afternoon. Rock solid 40psi, 13.4 volts at relays/pump. Got up to 180 degrees, about 10min. idle,

high idle, revs below 2800. Relays are warm to touch, pump is cool, pre filter is ice cold.

Still as confused as ever. Since I am along tonight, will wait before venturing to get past driveway.

BTW, changed nothing.

 

B&G

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Stuff to check.  Highlighted the non-electrical.  Note also that their web site says the pumps are rebuildable to "as-new" condition. Polymer wear plates worn, perhaps. 

 

Q. Why is my fuel pressure too low, or I have no pump pressure? 
A. Check the voltage to the pump, relay switch. Could be faulty. They can be bad without going out. Weak relay reduces voltage. Replace them. Check wiring, look for an improper ground. Check the battery voltage. Check the filter and inlet line for obstructions. Look for leaks on inlet side. Adjust bypass. Is there debris in pump bypass (poppet). The bypass valve could be stuck open. Clean filter. Replace deteriorated fuel-cell foam. If no pressure, the pump may be operating in reverse. Check the wiring diagram. No fuel in fuel cell, or fuel cell improperly vented. 

 

http://magnafuel.com/support/index.htm

 

http://magnafuel.com/products/efi/pumps/MP-4301.htm

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A mistake to even try what??

Your back-ass answer to a simple question is useless at best.

I had questions to the function of fuel pump relays, sorry if that is not interesting enough for you.

I have said it before...enjoy your posts, even your strange sense of 'humor' and finally your knowledge about

Datsuns.

What I don't enjoy or even need is BS. Look, don't look, could give 2 sh^ts...if you have something to add please do so in a non-puzzle like manner.

If you even read what I said the problem was posted not only for myself, but for anybody else(with all the V8

power out there) with a high flow, big HP fuel system....no matter what brand used.

Some people like to hear themselves talk, I guess you like to see yourself type.

Rant over...relays/filter cleaning will begin tomorrow.

 

B&G

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Just finished with relay change and filter clean. A little worried after changing relays that voltage was the same as

before....cleaned pre-filter(75 micron), which involved a tank draining, no real blockage and just a few pieces of 'dirt'No water in tank. Regular filter(25 micron) was slightly dirty, still not blocked.

End result....pump now builds psi on prime, fired right up, keeps consistent psi and 'Happy Father's Day' she made it

past the driveway and cruised around town/highway.

Now I can actually do some work that is not repairing something. Muffler delete is up first.

 

Thanks to all who offered help.

 

B&G

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