motomanmike Posted November 18, 2012 Share Posted November 18, 2012 (edited) Well, I finally got my car started on MSII E however I'm getting back to some basics I guess. My fuel pump is either toast or its not priming right. I have a 240z with a 76 280 tank, walbro pump. Here is how it is plumbed for the feed. At first I didn't have an issue, well I don't think I did. I'm not sure and have not played with lowering it down below the feed line but i'd like to keep it shielded which is why I mounted it where it is. The pump currently whines really bad and its not a constant whine, its up and down almost like a siren and will not pull fuel. I even dumped another 5 gallons from a dump can in the fuel tank thinking it was just out of gas with no change in the way it sounds. Here is what I have, 1/2 AN line feeding, 100 micron filter, to the pump, then 1/2 AN line up to the rail. Should I eliminate the 90's? The pump came with two small barbs I can't really see why the 90's would starve it? Are any of you running a similar set up that might have some insight? I can't tune this thing right until I figure out whats up with the fuel feed at the moment. The old yellow tube is on the old return line so it didn't get plugged with gunk. Edited November 19, 2012 by motomanmike 1 Quote Link to comment Share on other sites More sharing options...
Nigel Posted November 18, 2012 Share Posted November 18, 2012 That looks pretty high up. Those pumps don't like to pull fuel, and you may have an air pocket trapped there. You can see how low I have my mounted in the picture below. Never had any issues... Nigel Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 19, 2012 Author Share Posted November 19, 2012 (edited) It does seem very much like it is an air pocket stuck in there. I wouldn't think having to pull fuel 1-2" in height would be that hard for it but I'm guessing it can be an issue, i'll unbolt it from its mount and lower it down unmounted just to see what happens and go from there. Nice set up Nigel that car is spotless underneath. Man it would be nice if its that easy. Edited November 19, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 20, 2012 Author Share Posted November 20, 2012 (edited) Nigel I lowered the pump well below the tank and feed line. Would there be an reason that once the pump got its prime that it should slowly loose it even with constant power? I did some testing. I pulled the return off the rail, made sure it was free flowing down the body of the car. Put a temporary hose off the return of the rail and ran it to a dump can. I then got the pump to prime totally, nice low tone grrrr. It would get a slow trickle out of the return, but same result the pump would slowly start to whine, turning higher in pitch as it went on. I'm sure without resistance it will pump fuel fine but it seems its just weak like it just can't keep up. I'm using the stock fuel pressure regulator. I guess from all that description my real question is with the pump constantly on, and not much blow by past the regulator, would there be any reason that it should lose its prime other than being a bad pump? I've got 1/2 ANl ine feeding the pump (now higher than the pump itself then from the pump a run of 1/2 line up to a reducer at the front frame support to 5/16 line, a filter from a pathfinder V6, then 5/16 from it to match the rail size. I'm using the original 240Z feedline for a return, reading your page you did for quite sometime until a nice pinhole sprung up. Alot of posts i've read many others had success with this but mine just won't keep solid pressure. Voltages are good at the pump, i'm running it with the relay board from MS, I hooked a jumper ground and postive directly from a the battery just to test that possibility with no change. Is it possible to suck air but not leak fuel out of one of the AN fittings or elbows? Edited November 20, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 20, 2012 Share Posted November 20, 2012 Maybe you just have a blockage between the pump and the rail's outlet. Have you tried disconnecting the line at various spots to see if the pump will pump at all? Also, I couldn't tell from your pictures, but you might have the fuel lines connected backwards, or the wiring. The pump will spin in reverse if the electrical connections are backward. It happens. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 20, 2012 Share Posted November 20, 2012 (edited) Air leaks at a connection upstream of the pump will kill suction head every time! What's in the filter? Edited November 20, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 20, 2012 Author Share Posted November 20, 2012 (edited) It will free flow fuel out the front before the rail if I pull the line off, and boy is that a rush I always thought a bad regulator on the rail would leak, can they stick shut? I can hear the regulator hissing once the pump gets its prime though. Edited November 20, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 20, 2012 Author Share Posted November 20, 2012 (edited) Wouldn't I see a fuel leak at that pressure though If I had an air leak? Order of business for me I guess is to install the gauge I had on initially inline and see whats going on with it. I took it out just to have less fittings inline. Any way to test the regulators flow? Can I just blow air out of the compressor through there or will that just ruin it? Edited November 20, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 20, 2012 Share Posted November 20, 2012 Just re-read your thread and see that you don't mention fuel pressure. Are you assuming that something's happening based on the pump noise, or the volume of fuel that you see coming out of the rail's return line? To know for sure, you should measure fuel pressure, and collect and measure the fuel that comes out in a known amount of time. It might not be "losing its prime" at all, maybe it's just a weak pump. Or it might be fine except for the noise. You need the numbers. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 20, 2012 Author Share Posted November 20, 2012 (edited) I will this week sometime. Just trying to get some ideas. I tested it before buttoning up everything and removed the gauge to save fittings. I need to install one permanent, maybe just buy a nice aeromotive regulator and mount the gauge on it. I hate to throw more money at it but if its what it takes i've committed this much time and effort it would be worth it. Its sooooo close to being able to tune it but I just won't even try driving it until I know the fuel situation is right. I've seen way to many friends let boost eat motors. Thanks for the thoughts guys, I'll see what I can figure out this week. Edited November 20, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 20, 2012 Share Posted November 20, 2012 On the suction side under draw from the pump even the smallest leak can make you loose prime. One function of the EVAP system on the car is to harness the pressure of expanding vapours to slightly pressurise the tank, and therefore flood the inlet to the pump. Somepeopleare so efficient removing their EVAP system, they neglect to remember the system also let's air INTO the tank (filtered) when the fuel level changes...if this function at a minimum is not maintained the tank can quickly go into a slight vacuum and that can be all it takes. I have seen the Bendix pumps literally collapse the filler necks and show zero fuel pressure. Open the gas cap and all's fine again. Suddenly the cap on the vapor line wasn't so sanitary. Been that way for years, but once the vapor hoses were all repaired, there was no way for air to get into the tank as it was sucked dry. Quote Link to comment Share on other sites More sharing options...
Xnke Posted November 20, 2012 Share Posted November 20, 2012 You have a bad fuel pressure regulator. I fought this EXACT issue with my stock regulator for almost six months before I replaced it with a new unit and it workes perfectly now. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 20, 2012 Author Share Posted November 20, 2012 (edited) I had suspected this and ordered one today, it will be here at 4:00pm. I'll put it on tonight and see what it does. I hooked everything back up the way it does with the return line off the rail still in the dump can, used a hand vac tool on the regulator and it didn't change the flow at all coming out of the return so thats when I decided to get one and try it. Here's a video for giggles. This thing sounds TERRIBLE. It started out before I hit record on the video with a nice low grrrrr normal sound. Then slowly into what it sounded like here. I should have left the camera on record another 40 seconds or so because it primed and got the nice low tone grrrr right after I shut it down. Hopefully I haven't ruined the pump but we shall see. Edited November 20, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 20, 2012 Author Share Posted November 20, 2012 We got a bingo on the regulator!! Nice. Sounds like it should now. Thanks again everyone. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted January 18, 2013 Share Posted January 18, 2013 I had problems with walbro pumps loosing pressure at anything over 12lbs boost with 440cc injectors.They really arent designed to pull any vacuem at all and will fail from cavitation.The oem fuel pump mounting point on the 280z will actually gravity feed a pump.I switched to a Bosch 044 pump and never had problems again. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted January 18, 2013 Author Share Posted January 18, 2013 I did get it ironed out and it simply was a regulator. Very strange the way it acted and the way the fuel pressure even read. I've lowered the pump quite a bit and haven't had another issue with the priming or fuel feed. Still not a big fan of how loud the walbro is but its not a DD so I can live with it. Quote Link to comment Share on other sites More sharing options...
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