Anyone had an issue with one or both fuelpumps. It seems I have one fuel pump which does not work. Listened through the gas tank and one of them are stuck obviously. No wonder there is no power. Only one bank running. What to do? Take both out and throw away? Take the faulty one out and try to fix it? Any suggestions at all would be appreciated. //B// Image Unavailable, Please Login
How can you tell by "listening through the tank" if one of your fuel pumps isn't operating? Are you SURE that one of the fuel pumps isn't working? Have you cracked open a fitting to check for pressure? There is a filtering screen inside of each fuel pump - possibly clogged? And of course the fuel filter itself may be clogged, but whatever happens on one side should happen on the other as well. The easiest things to check are the two fuses and the two relays in the footwell panel. At least the pumps are reasonably easy to get at, but I would check a few things first before condemning the pump. Of course, be very careful about sparks and smoking if you are working on the fuel system.
You would wanna hope that there isnt that much crap in your fuel tank to block up the fuel pump gauze. Bugger that!!! My money is on the relay or the fuel pump has sh*t itself. Can happen.
I had a problem with my fuel pump once (not a Ferrari) and I replaced it, along with the distributor and fuel pump fuse. None of that did the trick. It turned out the ground wire to the fuel pump was loose. Although, the fuel kill switch I installed was shorting out too which added to the problem. I think by listening to the tank he means listening to see if he can hear the fuel pump "hum" noise when he turns the key to auxiliary, but I could be wrong.
The fuel pumps on a 348 don't run when you turn the key to the "ON" position. According to the manual, the ECU does not signal the pumps to run until the engine is cranking over at least 30 rpm on the starter. It would be very easy to rig up a jumper wire that would bypass the fuel pump relay and send power directly to the pump (for test purposes only). The fuel pressure regulators maintain pressure in the fuel rails after the engine is shut off (if the pump is working and the regulator is working), so cracking open a fitting with the engine completely shut off should tell you if the pump is pressurizing the system on the bank in question. I'm just offering up some ideas. To me, it has not yet been proven that the fuel pump is faulty.
I agree that the 348 WSM says that the fuel pumps don't run until the engine is turning greater than 30rpm (e.g. via the starter), and if that is actually true you'd think that we'd be able to test said claim by measuring the fuel pump relay output voltage as 0 volts when the engine is off while the ignition key is in Position II (i.e. Run, not Start). (or do 348's have an independent fuel pump cut-off device??)
On my previous 348, I had a fuel pump go bad. I took that piece of dog meat out and threw it way. Put a new one in. All was bliss. As for replacing BOTH of them... If you break your windshield, do you replace the rear glass too just for good measure?
Depends what was wrong with the fuel pump that failed. If it just went t's up and died, then it's fine to replace just one. If it was jammed with crud, or rusted, then I'd replace both of them. In your case, all was bliss with just one new pump, and that's fine.
It's very easy to do the electrical checks at the footwell panel. Let's say you're checking for power to the fuel pump on the right bank (1/4). You're looking at relay "N" (3rd from the right on the lower row) and fuse 19 (6th from the left on the lower row). It's important to note that the electrical power flows through the relay, to the fuse, to the pump. It does NOT flow through the fuse, to the relay, to the pump. So the first test is to hook up your test light to fuse 19. It will show no power when the key is off, and no power when the key is in the "run" position before you start. But once you turn the key to the "start" position and the engine starts to crank, then you should have power to the fuse immediately, and from there to the pump. Once the engine starts, the power to the fuse is constant. You can run power directly to the fuse, even if everything is shut off, by removing relay "N" from the panel, and using a jumper wire to connect terminal 30 (battery power, the top terminal) to terminal 87 (the bottom terminal, runs to the fuse). Once you do that, you should hear the pump running. The same test for the left bank (5/8) uses relay "C" and fuse 8. If you can't hear the pump running when you do this, then either: - There is no power at terminal 30 - The fuse is blown - There is a break in the wire between the fuse and the pump - The pump is dead - The pump isn't grounded Terminals 85 and 86 on the relay use the signal from the Motronic ECU to close the contacts between terminal 30 and terminal 87. This may sound complicated, but these are very simple steps. Edit: This picture shows me checking for operation of the oil cooler fan motor. It's exactly the same test for the fuel pump on the 1/4 bank, except using the relay next to this one. Image Unavailable, Please Login
Last year when I was looking at the M2.5 schematic for Plugzit, it looked to me as though it was the MAFs that gave the signal for terminals 85/86. Was I in error when I interpreted that, or did this change from MAFs to the ecus for M2.7?
I don't have an exact answer to that question. What relay were you looking at? The terminal numbers are the same on many relays, but I don't think the MAF's would have anything to do with the operation of the fuel pump relays. In this case I think 85 and 86 would get signals from the Motronics based on RPM readings from the crank sensors. The wiring diagram isn't that specific, but we know that the fuel pump relays aren't triggered until the engine reaches 30RPM, and I don't think the MAF's are capable of reading RPM's.
I've pulled up the schematic and I see what you said instead of what I was trying to remember. 85 on the relay N is controlled by pin 3 on the Motronic ecu. 87 on the relay N energizes fuses 19 and 20. 86 on the relay N goes to 87 on relay I as well as to 37 on the ecu and 5 on the MAF and pin 2 on all of the fuel injectors.
Aye. With his car started he should see ~~ 12 volts at fuses 19 & 20. If not, then the problem is with a signal or relay. If yes, then the problem is toward or with the fuel pump.
As far as we can see the current to the fuel pump is ok, which indicates there is something wrong inside. We will take both out and run them "dry". Both filters were changed last service,,,,,,1000 miles back and besides they are after the fuel pump. Taking out the fuel pumps gives one benefit more.........a clean gas tank. Seems that a fuel pump is not easy to get to.......at least not here in Sweden. Do we know anyone who keep them in stock? More info later. //B//
Can you please do me a favour Ben? DO NOT POWER UP USED FUEL PUMPS DRY!!!!! If you are thinking of doing that mate,(If understand your post correctly), please dont!!! The fuel pumps may and probably will explode! Have seen/heard it done before, causing serious injuries! Once a fuel pump has been used in tank, NEVER remove it and test it/power it up on bench. The little sparks from the electric pump, coupled with the fuel/vapour left inside the pump will make it explode. DANGEROUS! If you are to test a used fuel pump removed from the car, fill a bucket/container full of fuel and drop the fuel pump in there. Make sure the fuel pump is totally 'drowned' in the container of fuel!! Honestly, dont even attempt to do this. The best way to test the fuel system is borrow/beg/steal a fuel pressure tester with flow gauge. Tee that into the fuel system and go from there mate. This checks fuel pressure and the flow gauge will tell you how much fuel flow you have. Most fuel problems will either have fuel pressure, but no flow. Or have fuel flow, but no pressure. Please try this 1st mate. Do NOT run them pumps on the bench dry buddy! Dont want you or someone else to get hurt!!
Was the current tested with the motor running, or only with the ignition key in Position II Run (but with motor off)?
I disagree with Pap's comment about testing the pump while it is submerged in a bucket of fuel. DANGEROUS!! DON'T DO IT!! NOT WORTH IT!! I agree with his comment "Honestly, don't even attempt to do this." I agree with his comment that the best way to test the output of a pump (if the pump is running) is with a proper gauge designed for that purpose, hooked up with a "T" fitting to the fuel rail. But if you have power to the pump (easy to test) and the pump is grounded (easy to test) and the pump is not humming, then your pump is dead and it needs to be replaced. It doesn't need a bench test. It most likely doesn't need the entire pump assembly (155699), it needs the pump motor (155592). This is just my opinion, I have never replaced a pump on my 348.
I will explain this a little better. Testing a fuel pump on the bench was one of the 1st things we learnt about when I started my apprenticeship. You do not do it. Simple as that!! Guys that have done it and not been hurt, have been very very lucky. They tend to explode and can catch fire too. I had a guy working for me once, around 5 years ago now that attempted to bench test an electric fuel pump in my workshop. I assumed he knew not to bench test them, but he thought you could. I saw him remove the pump, which he diagnosed as not working at the time (similar senario here) and then he walked over to bench. 10mins later, I see him cutting and joining wires, as if he was ready to power it up. I yelled out at him to stop doing what he was doing. I went over and asked him what was going on and he replied that he wanted to power it up to check that it was working. Bad move!! I told him what could happen and he didnt believe it. So............we took the old pump out the back, wired it up and unrolled a few metres of 2mm electrical wire around the corner out of harms way. We powered that sucker up using a car battery and the pump "whirred and whizzed" for around 2 seconds before it went BANG!! It blew apart like a CFC can in a fire. It split the fuel open pump and most of the internals were nowhere to be found. Was a loud bang too, like a shotgun blast. Scary sh*t!! That also told us that pump was working, so he diagnosed it wrong anyways! It was faulty/worn wiring to the fuel pump relay. So we paid for the new fuel pump and repaired the wiring to the fuel pump relay. If he powered that pump up on the bench, standing in front of it, he may have lost both eyes or worse! Never do it guys! I have also heard a few stories of "backyard" mechanics doing this at home in the garage and causing themselves injuries! Alot of people are unaware of this. This happens because of the fuel vapours inside the pump (highly flammable) which pressurize when the pump is powered up causing the pump to explode or catch fire. PAP SAYS............DONT DO IT! If the pump is getting power but is not working, then the pump is stuffed 99.9% of the time. Testing the way Miltonian described the best way.
See, that just goes to show you that the 348 Brotherhood cares about keeping people out of harm's way. Pretty cool to see that kind of compassion for strangers that we've seldom or never met. I dig it.
I will explain this a little better also. You can and I have, tested these before in buckets of fuel. There are a few ways to do this. But in all honestly, there should be no need to 'bench test' any fuel pump, as you can normally just crack the fuel lines in the car ect........as most on here already know. But.......I usually get a bucket half full of fuel. Wire up the pump, submerge the pump in the fuel. The pump must be 110% covered in fuel!!! If not, add more fuel. Then have the other end of the wires and battery at least a few metres away from the bucket of fuel. All you have to do is, power the pump up for 1 micro second, just till you see/hear the fuel slosh around in the bucket. That will tell you that the pump is working. Simple as that. If you sit there like a dickhead powering it up for a few seconds, then of course it will spray fuel everywhere and do more harm than good. The other way is exactly the same, but you put some fuel hose on the outlet of the pump and run that hose into another bucket or bottle/fuel can so when you power it up, the fuel does not spray everywhere and you can run the pump for a few seconds if need be ect...... But 99.9% of the time, there should be no need to bench test pumps.
Sage advice PAP, and we will be sure to follow it, at least I will anyway. No bench testing the fuel pumps.
