grretc Posted July 25, 2012 Share Posted July 25, 2012 I recently picked up a 1975 280z to build into a nice weekend warrior car. I'm stilling working on another motor for it so for now it sits..but not for long...While I'm building my other motor to put in it, I thought I would at least get it into running condition so I can enjoy it for a little before school starts. When I bought it from my friend he told me that the car wouldn't go over 40 mph because the injectors are clogged and that the gas tank is rusty, that's why the injectors are clogged. When I sold the same exact car to him a couple years ago, the injectors weren't clogged. Everything works fine, except it doesn't want to go over 40 mph. The car will crank for a bit, then start and idle just fine. It will rev..just fine and shifts into gear just fine. It's completely stock.. So is it true? Are my injectors clogged and filled with rust? That's why it won't go over 40mph? That's on a lucky day too most of the time it's 30mph. It will go up to 40 and I can just keep gassing it but 40 mph is where it wants to be. Do I need to replace the injectors? Or is there another way to clean it out? Or is this not the problem at all? Could really use the help. I just want some reinforcement before I go through the hassle of replacing the injectors. Thanks HybridZ Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted July 25, 2012 Share Posted July 25, 2012 How does it act when you're at 40? like do the rpms hit a wall, or do the rpms climb and it just doesn't do anything? You should ask you're friend if he did any mods to the car, or where he was taking it to if he wasn't doing the work. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted July 26, 2012 Share Posted July 26, 2012 Remove the fuel filter and try to blow through it, You should be able to easily blow air through it, if not it is clogged. Try that. Quote Link to comment Share on other sites More sharing options...
JSM Posted July 26, 2012 Share Posted July 26, 2012 Does it back fire at all? If you know there is rust in the tank you will have to pull the tank flush, clean and seal it, plain and simple. Your highly likely running lean and the car simply can't be supplied enough gas under load. If u don't clean the tank, you will have the same problem with the new motor. Likely the injectors are gunked and nut rusted clogged. Unless you don't have a filter on the supply line to the injectors. Additionally you will need to check the screen on the fuel pump. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 26, 2012 Share Posted July 26, 2012 (edited) A fuel pressure gauge mounted where you can see it while the problem happens will let you split the problem in to pieces. If fuel pressure stays in spec., the problem is not with the tank, pump, filter, lines or FPR (although they might still have problems), so injectors might be the problem (still no guarantee). If fuel pressure drops out of spec., creating a lean condition, then look at those things and get the fuel pressure back up where it should be. Fuel pressure control at the injectors is so important it just makes sense to measure it first. Just one more opinion from a guy who likes to see the numbers. Edit - don't forget the other half of fuel supply either - air. Maybe there's a mouse living in the air filter housing. Edited July 26, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
eddieeats Posted July 26, 2012 Share Posted July 26, 2012 JSM is correct drop and clean the tank before you go spending money on other stuff then change the fuel filter and also put a fram G3 clear fuel filter between the tank and the fuel pump that will let you see how clean it really is. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 26, 2012 Share Posted July 26, 2012 Still sounds backwards. Fixing something that you don't know is broken. But these cars are mostly time-filling hobbies anyway, so have at it. Rebuild the engine while the tank is out, it probably needs it anyway. Can't hurt anything but the wallet. Quote Link to comment Share on other sites More sharing options...
JSM Posted July 26, 2012 Share Posted July 26, 2012 Still sounds backwards. Fixing something that you don't know is broken. But these cars are mostly time-filling hobbies anyway, so have at it. Rebuild the engine while the tank is out, it probably needs it anyway. Can't hurt anything but the wallet. I would agree 100% if he said the tank wasn't rusty. I went through this process with my 280z. I did your route first as it is the easiest. Inline gauge right of the injectors. Actually it's still in the car. The hard part was at idle the car and pressure were great. Give it gas and try and drive it, forget it. Mine backed fired a lot though via the intake. Now if I had a camera where I could see what was going on that would have been great but either way the tank was coming out! The amount of rust was unbelievable. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 27, 2012 Share Posted July 27, 2012 Well, he has a variety of paths to choose from. Let's see which route he takes through the maze. I'm assuming it's an automatic, since the problem is apparently speed, not RPM, related. Could be another clue. Quote Link to comment Share on other sites More sharing options...
grretc Posted August 1, 2012 Author Share Posted August 1, 2012 Thanks everyone for their input. I drove to the gas station and put fresh gas in the tank. Car runs like a champ now. Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 1, 2012 Share Posted August 1, 2012 That's it? The whole problem was "bad gas". Might be the most effort for the easiest fix ever. Quote Link to comment Share on other sites More sharing options...
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