DuoWing Posted June 16, 2012 Share Posted June 16, 2012 (edited) Alright I have been going round and round with this for a while now, but I can't quite seem to solve this issue. I'm running the Bosch 044 inline pump. No filter in between pump and tank. Anyway after driving for a while particularly freeway driving for a little while I can get off the freeway and suddenly my fuel pump will be really loud. Generally when this happens fuel pressure has dropped as well. I'll be checking the underhood rail mounted gauge at idle and I'll see usually idle pressure is down from where it should be. Generally almost 20 psi vs 25-27psi. Also I've noticed the relays will be pretty hot. I still don't know how warm/hot relays are supposed to get when running for a while. I know the relay for the parking lights with the upgrade gets pretty warm itself after running for a while. Anyway I ran a 12 gauge wire from my Maxifuse blocks to my Fuel Pump Relay. No difference. Swapped in a 20/30amp Tyco Relay and it seemed to still end up doing the same thing. JeffP was telling me to go to a junkyard and look for earlier Infinitis that have ABS, as they have a generally larger Bosch relay with much larger connections that should be better off for supporting something like the fuel pump. Anyway I couldn't find what he was talking about, but I found a set of larger relays on the Quest that is used for the Quest's ABS system. The relays use a rounded pin connection so I took the relays and block and swapped those in. It's a a set of 2 Bosch relays one being a 6 pin relay and the other is a 4 pin. It says that they are 50amp relays so I figured this should be enough to support the Fuel Pump wiring. It seemed to last a good while, but still eventually the pump started to get louder. Although I did notice this time it looked like idle fuel pressure was just about 25psi maybe slightly lower, so an improvement. I was seeing at most 14.1v into the relay, about at most 13.9v coming out of the relay, and finally about 13.1v all the way back at the pump. Stupidly I didn't test the pump voltage right when I started the car to at least see if it's getting higher voltage when the relay is cool and everything is running. One thing I haven't done is redo the pump wiring. I'm still running the original wire from the 76' body from the pump all the way to the connector near the passenger seat. From that connector I then have a newer wire running to the relay. I'm just looking for some advice. I figure the next thing maybe even the necessary thing to do would be to re-wire the pump ground and power to be at least 14 gauge wire running straight to the the relays with no interruptions. As for fuel system, I'm running a pretty much stock L28ET motor with the Z31 ECCS setup. Also do you guys think these relays would be sufficient enough? Edited June 16, 2012 by DuoWing Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted June 16, 2012 Share Posted June 16, 2012 I don't think the wiring is the problem. The current draw will increase as the wires heat up and increase their resistance, but this shouldn't effect the pump unless it's really not getting enough voltage. I believe I am having the same problem. My new Aeromotive pump got mighty loud after a 30 minute tuning session. My previous pump was also loud (all the time though), and then it died. I had a pre-pump filter on the previous one, and I have a nice Jeg's filter on this one. However, I think my problem is that the fuel tank feed--the portion in the tank is getting clogged. I cleaned this tank before I put it in but I think I'm going to run it real low and then take a look through the fuel sending unit's opening. I don't know if there's a screen on the fuel outlet (that is, the feed to the pump) in the tank, hopefully someone else can chime in? I have a 77 tank, I imagine it's different throughout the years. Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 17, 2012 Author Share Posted June 17, 2012 I had my tank professionally cleaned and reconditioned, but I don't know with this. I'm almost debating doing what was said in that thread in the FAQ section about running a smaller low pressure pump prior to the main pump. Quote Link to comment Share on other sites More sharing options...
MazerRackham Posted June 17, 2012 Share Posted June 17, 2012 Its called a surge tank. DO IT Quote Link to comment Share on other sites More sharing options...
Oddjob Posted June 17, 2012 Share Posted June 17, 2012 (edited) Well, here's the science of it: There are two reasons for your relay to be hot. The coil that holds the relay closed will dissipate some heat. This is normal, and will have no effect at all on your fuel pump. The other reason is resistance across the contacts. A tiny amount is normal, but as you say you have a 0.2vdc voltage drop across the contacts, this could indicate a problem such as pitted contacts. The repair is to file the contacts smooth, and then burnish with emery cloth, assuming you can get inside the case. A new, good quality relay should show an unmeasurable voltage drop across the contacts, at least with a hobby-quality VOM. What is of more interest is whether your pump is hot. The lower the voltage you supply to the pump, the higher the current (amperage) will go, creating more heat. The voltage drop to your pump is governed mostly by resistance, and that is chiefly a function of distance and wire size. The stock wire run to the rear is almost certainly too small a guage for a performance application. I used 10AWG on mine (a Holley red-top), without a relay, from the 12v source all the way to the pump. Another problem is the return path (ground). I measured the resistance across the stock return path and found it around 36 ohms. This results in a substantial voltage drop at the pump. Since I have star-grounded most of my car, the pump now has a dedicated 10AWG run back to the ground bus near the battery (resistance = 0 ohms). Most of the details of all this are posted elsewhere on Hybrid Z. My initial reaction is that your pump is heating up after being run awhile, due to voltage drop. Since the Bosch 044 is air-cooled you can easly check it after a run on the freeway on a warm day. When a pump becomes heat-soaked, its performance changes for the worse. Edited June 17, 2012 by Oddjob Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 17, 2012 Author Share Posted June 17, 2012 (edited) Well, here's the science of it: There are two reasons for your relay to be hot. The coil that holds the relay closed will dissipate some heat. This is normal, and will have no effect at all on your fuel pump. The other reason is resistance across the contacts. A tiny amount is normal, but as you say you have a 0.2vdc voltage drop across the contacts, this could indicate a problem such as pitted contacts. The repair is to file the contacts smooth, and then burnish with emery cloth, assuming you can get inside the case. A new, good quality relay should show an unmeasurable voltage drop across the contacts, at least with a hobby-quality VOM. What is of more interest is whether your pump is hot. The lower the voltage you supply to the pump, the higher the current (amperage) will go, creating more heat. The voltage drop to your pump is governed mostly by resistance, and that is chiefly a function of distance and wire size. The stock wire run to the rear is almost certainly too small a guage for a performance application. I used 10AWG on mine (a Holley red-top), without a relay, from the 12v source all the way to the pump. Another problem is the return path (ground). I measured the resistance across the stock return path and found it around 36 ohms. This results in a substantial voltage drop at the pump. Since I have star-grounded most of my car, the pump now has a dedicated 10AWG run back to the ground bus near the battery (resistance = 0 ohms). Most of the details of all this are posted elsewhere on Hybrid Z. My initial reaction is that your pump is heating up after being run awhile, due to voltage drop. Since the Bosch 044 is air-cooled you can easly check it after a run on the freeway on a warm day. When a pump becomes heat-soaked, its performance changes for the worse. That's an interesting take on it and something I'll have to check. I know even when it's noisy the pump maybe feels slightly warm to the touch if that. At least nothing to the point that I noticed there being a problem. I'm thinking I'll have to change up the wiring for sure. I've started to build a star ground setup for my car. I didn't do too much, but as of right now I do have a ground setup running from the firewall to the negative terminal of the battery. I ran another to my grounding point for my HIDs and then a third running to the other side of the car which I intend to branch off for the ECU and main harness. I'll probably now run one to the back of the car for the rear lights and I could then connect the fuel pump to this with larger wire. The surge tank + low pressure pump is something I will probably add as well. I remember the shop that did the tank mentioning they cut out some kind of baffling or screen that was in the tank as when they blasted the tank that it fell apart or was really too small to properly blast and keep in tact. So I don't know if this could contribute? As for the relays I'll have to play around and see if I can clean up the contacts more and see if I can result in lower voltage drop. I would definitely think though that part of the issue in the drop I'm seeing probably comes from using an auto-ranging voltmeter which makes it hard to get a more definite reading. As for the relays themselves I feel like they should definitely be a better upgrade for the fuel pump. Thanks for the info though. It's something I'm going to work with and see if the wiring + relay contacts can improve the situation. Also here's a few pics comparing pretty much what I was using to the new relays I'm using. Edited June 17, 2012 by DuoWing Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 18, 2012 Author Share Posted June 18, 2012 (edited) Well almost done rewiring the pump. Routing the wiring through the interior of the car and the quarter panel was a pain, but I managed to get it through so it all looks relatively stock. Did brand new 10 gauge wiring from pump negative terminal to where the tailights ground in the back. The power wire is a straight shot from the relay in the passenger foot well to the pump positive terminal. So at the very least as was mentioned I should be seeing a much smaller to no voltage drop back at the pump which I'm hoping finally solves my issue. I would have tried driving the car except my mini-torch ran out of butane as I was going to make the last solder connection and now it's about to rain... Well other than having a heck of a time trying to solder 10 gauge wire everything is finally connected up. I'm not happy with the solder joint from the relay to the pump. I think I'm going to have to redo that. Does rain/high humidity make it harder to solder? Anyway it was a downpour outside so I didn't take the car out for a drive, but I started it up and let it idle. With a different voltmeter set to 20 DCV I was seeing about 14.1-14.15 coming from the relay. Back at the pump I was seeing about 13.85v. I wish I would have measured on the original wiring when everything was coming from a cold start, but I would definitely say seeing as the pump has a much shorter direct to chassis ground with 10 gauge wire vs. the old tiny wiring, along with much larger wiring feeding the positive and I'm still seeing 13.85 I can begin to see what was mentioned about the old wiring being definitely too tiny. Really hoping this finally solves my problem. Edited June 18, 2012 by DuoWing Quote Link to comment Share on other sites More sharing options...
Oddjob Posted June 19, 2012 Share Posted June 19, 2012 (edited) With the changes above, you are now at a voltage drop of 0.3vdc at the pump. This is really pretty good, and I will bet it represents a considerable improvement over the stock wiring. I think you will see a further improvement when you run the star-ground lead you described from the firewall to the taillight ground buss. With any luck, all of this will fix your problem. If not, at least you have eliminated the prime candidate. Good luck. Edited June 19, 2012 by Oddjob Quote Link to comment Share on other sites More sharing options...
gmanatc97 Posted June 19, 2012 Share Posted June 19, 2012 I am also having a problem with my fuel pump wiring. Seeing how you are neck deep in it maybe you can help. Three years ago when I got the car it didn't run. Thought it was the relay under the passenger seat so I bypassed it and now my pump runs constantly. I have read the fuel injection bible and a few other threads, and it seems that to that relay there is a wire from the distributor and the AFM, right? Those are what tells the pump to run, correct? I have a blue and a green with a yellow strip coming out of the harness where the relay was. And the relay looked exactly like the one in the picture in your last post. Then I have the red and black ones going to the pump, pretty sure they are not original. Where did you get your new relay and which wire goes to which post on the relay? Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 20, 2012 Author Share Posted June 20, 2012 Depending on which relay you're asking about, the bigger one I pulled from a 96' Nissan Quest. It was a box labeled ABS. I pulled the relay, along with the relay connector and everything so I could wire it up. The smaller relay, I ordered through Amazon. http://www.amazon.com/gp/product/B000P61E36/ref=oh_details_o01_s00_i00 Unfortunately I'm not sure how the wiring works for the 280Z fuel pump. It's been a while since I've even had my fuel pump relays even wired the original way. I've been using the Z31 ECU setup for a few years now. The pins are numbered on the bottom of the relay. The main power for fuel pump goes to pin 30 and then the power that then goes from relay to fuel pump is attached to pin 87 I think the number is. Then the 2 wires that trigger the relay would go to 85 and 86. From what I remember at least is that the green wire on the 280Z is what went to the pump. I think the blue is what feeds the main power to the relay. Unfortunately you'd have to look through some wiring diagrams. Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 21, 2012 Share Posted June 21, 2012 I am also having a problem with my fuel pump wiring. Seeing how you are neck deep in it maybe you can help. Three years ago when I got the car it didn't run. Thought it was the relay under the passenger seat so I bypassed it and now my pump runs constantly. I have read the fuel injection bible and a few other threads, and it seems that to that relay there is a wire from the distributor and the AFM, right? Those are what tells the pump to run, correct? I have a blue and a green with a yellow strip coming out of the harness where the relay was. And the relay looked exactly like the one in the picture in your last post. Then I have the red and black ones going to the pump, pretty sure they are not original. Where did you get your new relay and which wire goes to which post on the relay? The early 280Zs, up to 78, used a contact in the AFM to complete a circuit to the fuel pump relay, which is housed in the same case as the EFI relay, by the hood latch release lever. In 78 they introduced a system that used the alternator L circuit and an oil pressure switch to control a fuel pump relay. The FSM gives the details. Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 22, 2012 Author Share Posted June 22, 2012 (edited) Well took the car for a drive today. Still did the same thing. Noisy and lower fuel pressure. After everything was all warmed up the relay was still getting hot, but I was still only seeing a .3-.35v drop between pump + terminal and the relay out so definitely an improvement in there. I also think the relay getting hot is really not as much of an issue as I thought. I turned the car off, pulled the hot relay and popped in a spare I pulled from the yard that was cool. I was still seeing the same voltage across the relay and to the pump. I need to run the ground wire for the star ground setup when I get some more time. I got a cheap Airtex low pressure electrical pump. So I think I'm going to go ahead and at least try for a dual pump setup to see if that helps. At least this pump is little so I can mount it horizontal. I don't know if having the Bosch or my Walbro mounted vertically causes a problem. My pump is mounted in such a way that maybe only half of it sits below the tank output, maybe this is part of the reason. Maybe these pumps really just don't like having to do any sort of pulling of fuel? Also I noticed that my Bosch pump leaks a little bit at the inlet to the pump. Either the fitting isn't tight enough or that washer that came with the fitting isn't acting like a very good seal. At least like was mentioned I've eliminated the wiring portion of this equation... Edited June 22, 2012 by DuoWing Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 26, 2012 Author Share Posted June 26, 2012 (edited) Well I cut up the original mounting plate for the fuel pump a bit more and now have my Bosch pump mounted horizontally in the exact same spot where the original pump was. Pump still did get a bit noisy, but I really couldn't hear it until I got back and into a quiet garage where the sound could be amplified. Also I think I fixed the leak at the pump feed fitting, also it was under 70 degrees today making it much cooler so that could make a difference. Overall at least pump noise seemed like a huge improvement. It could simply be that these things do not like vertical mounting. I'm thinking I might try and get some metal and make a bracket to mount the pump just a little lower so the entire pump body will be below the fuel tank output barb. Edit: I kinda keep forgetting that the pump is more than likely going to make noise no matter what, I'm just not sure how loud a pump should normally be. I also don't know if my regulator could be partly to blame? Anyway today when I finished my drive I was sitting at about 25psi which is spec for stock L28ET at idle, but when I pull the vacuum line from the regulator it's only hitting a little over 30psi. When the car is cold and has sat for a few hours I can go hit the key to do the 5-second prime and my gauge will be hitting nearly 40psi. I would think pulling the vacuum line should cause the fuel pressure to jump to where I have the regulator set at. Edited June 26, 2012 by DuoWing Quote Link to comment Share on other sites More sharing options...
DuoWing Posted July 23, 2012 Author Share Posted July 23, 2012 Well it's been a little while. Did a 100+ mile drive in the Z today, farthest I've driven it since the motor swap. Anyway I mounted the fuel pump a little lower since last time, but I feel like I could still go a little lower. It was in the high 80s maybe 90 degrees today and I got off the freeway after about 50 miles to stop and get gas and just like normal I could hear the pump whining away. I don't know why it gets so loud. Fuel pressure still drops a little, but sitting lower and horizontal has helped. I drove it the remaining 50 some miles back with no problem and even got on it pretty good at times. Had no sputtering/loss of power issues so the car seems to be running really good. I ran it up to over 5k in 4th gear so I should have seen some sign of problems if the fuel pump would start causing problems. I just wish I could figure out why the pump gets so dang loud. Or how to remedy it. Quote Link to comment Share on other sites More sharing options...
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