Zcardiesel Posted July 10, 2010 Share Posted July 10, 2010 I have a Zcar that has the L28E engine with the EFI fuel system and wanted to ask what is the best way to test the fuel pump? I have a "no start" issue with the car where it will not start, but will crank forever provided there is enough battery power. I haven't had much time to look at it to diagnose the problem and I don't have a manual for the car to refer to, but I really think I'm dealing with an original pump that is just dead. When you turn the ignition switch to the "ON" position you don't hear anything at all from the pump and it's just quiet like nothing is going on as far as flow. Put all new filters on the car including the fuel filter, and when removing the fuel hose off the outlet side of the new fuel filter it was bone dry after cranking for two or three 20-30 second intervals. Not even a hint of gasoline smell from the hose either. Got under the car today to locate and look at the fuel pump to check to see if anything looked out of place and everything looks OK and wiring is not damaged or chewed. It has two wires coming down to contact studs on the pump itself and one wire is a green w/ blue stripe and the other is wire is black. Can I remove the wires from the studs and apply 12 volts directy to the correct studs on the pump with a good battery? I figure that's about the easiest way to test, if there isn't a better way of course. The car has low miles for the year, so I'm sure it has to be something simple and the fuel pump really seems to be the bad part. Thanks for any help. Sal Quote Link to comment Share on other sites More sharing options...
Two80z4me Posted July 10, 2010 Share Posted July 10, 2010 same problem, it was the power wire going to the fuel pump, me being american and lazy wired in a new relay from the battery to a switch, and from a switch to a walbro 255lph pump. works great now, not one more problem since. Quote Link to comment Share on other sites More sharing options...
Challenger Posted July 10, 2010 Share Posted July 10, 2010 Check the fuel pump relay. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 10, 2010 Share Posted July 10, 2010 Here at this site - http://www.xenons30.com/reference.html - are free downloadable manuals that some Z enthusiasts have made available to anyone with the time to download. They all have extensive sections on fuel, with diagrams and testing procedures. Most are indexed in to folders except the 77 year. Definitely worth the effort. 12 volts direct to the correct terminals would tell you if the pump is bad. Or a voltmeter at the terminals would tell you if you're getting 12 volts when the key is on Start. I would do the second, voltmeter route, first, you'll either get 12 volts and know the pump is bad or won't get 12 and you can focus on the relay, wiring, etc. Plus there's less risk of an inadvertent short, playing with hot wires. What year car? Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted July 10, 2010 Author Share Posted July 10, 2010 Thanks for the replies. The car is a 76 280Z, the one listed in my signature. NewZed thanks for the link and helpful advice and I do think after I test the fuel pump that the fuel pump relay would be the next thing to check or test. I have a factory 1982 Datsun Maxima workshop manual that goes into good detail about testing the EFI and fuel pump relays by checking certain pins on I think the control unit harness plug. I just hope it isn't the ECU (control unit) because that's probably not cheap to replace. That's the closest workshop manual I'd have to the Zcar and the Maxima uses the L24E engine, which is really very close if not having the same fuel system as what the bigger 2.8 has in the Z. So, I want to test for 12 volts at the fuel pump terminals w/ the key in the "START" position right? Thanks again. Quote Link to comment Share on other sites More sharing options...
goodoldjam Posted July 10, 2010 Share Posted July 10, 2010 (edited) Check out this post http://forums.hybridz.org/index.php?/topic/28500-75-280z-fuel-pump-trouble-quite-long/ Apparently it sounds as though the car doesn't prime. It only activates when air is flowing through the AFM. So according to that it needs to be cranked for you to check it. OR power from under the car. Edited July 10, 2010 by goodoldjam Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 10, 2010 Share Posted July 10, 2010 Check out this post http://forums.hybridz.org/index.php?/topic/28500-75-280z-fuel-pump-trouble-quite-long/ Apparently it sounds as though the car doesn't prime. It only activates when air is flowing through the AFM. So according to that it needs to be cranked for you to check it. OR power from under the car. That's right, the 76 has a contact in the AFM to run the fuel pump relay, for safety. It is bypassed at Start. So you can either put the key at On and prop the AFM flap open to run the pump or pull the small wire on the starter and hit Start. Zcardiesel, I didn't see your sig because I wasn't logged in when I read the post. Sigs only show when you're logged in apparently. And they don't show when you're on the Reply page. Sorry about that. Good luck. Don't start any fires... Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted July 13, 2010 Author Share Posted July 13, 2010 Well, took a look at the car on Saturday a little bit and first thing I did was go out and remove the black plastic cover on the AFM. I turned the flap assembly so the arm was not contacting the contact to disengage the fuel pump and tried starting and still no start. I also looked at the "EFI bible" that I found through one of the links above and it is pretty much my answer to diagnosing the car to get it running. One of the first tests they want you to do is when you turn the key to the "ON" position put your hand over the combo EFI/fuel pump relay at the top left kick panel to hear/feel if it clicks or not. Then the steps for testing afterwards depends on if it does click or not and I found that my relay assembly does click when key is turned to "ON". The only bad thing is I'm not too good with reading wiring diagrams so it might take me a long time to get this thing figured out. The next step I have to do is remove the 35-pin harness plug at the ECU to do tests at certain pins to eliminate each component that's good to find what's bad. I'm just too excited to get the car running, but know it will take time testing the ECU harness plug. And wow for a 75-76 car and electronics this is really kind of ahead of it's time as far as the EFI system is concerned. Thanks for all the help provided and will keep you all updated. Sal Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted July 14, 2010 Author Share Posted July 14, 2010 Another update, tested for voltage back at the fuel pump wires and with my sister cranking the car over to the "START" position I am getting voltage back there but it's only about 8 volts. Battery is good and makes about 12.4 volts sitting there, so does the fuel pump need to see at least 12 volts or can it run on that lower amount?? Using the EFI bible I found that my fuel injection relay does click when the key is turned to the "ON" position and did all tests afterwards on pins 1 and 10 for battery voltage, 5, 16, 17, and 35 for good continuity, and tested pins 14, 15, 30, 31, 32, and 33 for battery voltage to the injectors. Only problem I had there was that pin #32 tested about 10.5 volts while the rest of the pins for the injectors tested at my correct 12.3-12.4 volts. But, I don't think I have any faulty wiring or a bad ECU. Getting only 8 volts back at the pump kinda worries me and after testing at the wire studs on the fuel pump I removed the wires and applied 12 volts from a good battery to the terminals and the pump didn't run or make any noise? Any thoughts so far and thanks. Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted July 22, 2010 Author Share Posted July 22, 2010 Any other advice on what I should do or should I just replace the fuel pump? Because that's what I'm thinking is the bad component on the car after doing all the testing I've done to this point. Thanks. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 29, 2010 Share Posted July 29, 2010 Getting only 8 volts back at the pump kinda worries me and after testing at the wire studs on the fuel pump I removed the wires and applied 12 volts from a good battery to the terminals and the pump didn't run or make any noise? Any thoughts so far and thanks. Thought: You have answered the question, /Obiwan Voice/ "Trust your instruments, Luke!" The only way testing works is if you believe what the tests have told you. This is the largest problem I have training people to troubleshoot. They follow the procedure, find the answer, then blindly look up and say 'now what'? You have followed the procedures. You have a component which fails the test. Replace the component. This is not a sarcastic commentary, but I KNOW you're thinking to youself right now: "It CAN'T be that easy, I found it so quickly." Yes, it really IS that easy! Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted July 31, 2010 Author Share Posted July 31, 2010 Hi Tony, and thanks for the very wise advice. I do have to agree it's almost like I haven't quite trusted myself in being confident in the diagnosis of the bad component. But I do have to say I'm going to go ahead and replace the fuel pump and see what happens. I do think I'll have a running car after it's said and done. Thanks and appreciate your post. Sal Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted March 20, 2011 Author Share Posted March 20, 2011 It has been a long time since I've tried to work on the Z to figure out the problem I'm having. I worked on it today and found when I pulled the solenoid lead off the starter, turned ignition to "start" that I got a sound back at the fuel pump to tell me that the pump is good or working fine. I held the ignition key to "start" for 45 seconds or so to see if fuel would be pumped up to the fuel filter but got nothing and still is bone dry. I did remove the #1 spark plug from the cylinder head to check for spark by grounding it to the valve cover and did spark when I tried to start the car. The engine is not priming as far as fuel is concerned. I think it's an electrical issue with a relay maybe. The power relay at the left kick panel area does click when the ignition is turned to the "ON" position and again when turned to "start". What is the easiest way to test the fuel pump relay? Can I remove it and test the resistance at the contact pins to find out if it's bad or not? With the solenoid lead installed on the starter and the AFM flap not touching the contact the car still just cranks. Any advice as this is my first gas car or truck I've worked on? Thanks. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 21, 2011 Share Posted March 21, 2011 (edited) I worked on it today and found when I pulled the solenoid lead off the starter, turned ignition to "start" that I got a sound back at the fuel pump to tell me that the pump is good or working fine. There are conflicting facts in your thread. Earlier you said that 12 volts direct would not make the pump turn, which pointed to a bad pump at the least. Now the pump turns (maybe, at least it makes noise) but fuel doesn't flow? I would start at the basics. Take the pump off and see if gas comes out of the tank, to confirm the inlet line is not clogged. Connect 12 volts to the pump and see if it turns. Hook up some hoses and see if the pump pumps with 12 volts (water or gasoline if you're careful with sparks). Prop the AFM flap open with the key On and measure voltage at the pump wires on the car. Etc. Somewhere along the way there will be a failure. Edit - the fact that it didn't turn the first time you connected 12 volts but you hear some noise now points to a worn out or rust-clogged pump, not an electrical issue. Edited March 21, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
Zcardiesel Posted March 22, 2011 Author Share Posted March 22, 2011 Thanks for your reply. Working on the car and figuring it all out has been on the back burner because I got about 2 or 3 other projects I'm working on at the same time. But, to clear things up this is with the good, used fuel pump I bought back in July (which is actually a turbo engine fuel pump, but it bolted right in place). And as a matter of fact when I replacd it the fuel line that goes from the outlet of the fuel tank into the pump did not pour gas out when I removed it. I got a brown looking fluid mix when it came out of the inlet nipple on the tank itself, so I think I do have a restriction right there that isn't going to allow fuel to flow like it should. What is a good treatment I can put into the tank to clean or free it up? Maybe that is my problem all along, but I should take the pump out to test it w/ 12 volts to see if it pumps gas. Oh, and in that earlier post when I applied the voltage directly to the fuel pump that was the original pump. I never did try to see if it would make noise with the solenoid lead removed from the starter like the turbo fuel pump I replaced it with does. Maybe my original pump was fine, so I'll have to test it to while I'm at it testing the turbo fuel pump. I hope it's the pump or the tank just clogged, as the electrical system seems to have tested fine so far. I will keep my progress updated. Quote Link to comment Share on other sites More sharing options...
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