Z-Heap77

Can you tell me which line in the engine compartment is a vent line? I'd line to try pressure testing the system that way as well.

Zed, We had done some mods recently which I had a post going for a while because we had a terrible time getting proper fuel pressure after the mods were done. We swapped to a non-egr intake and palnet fuel rail. We installed new injectors, FPR, pump, filter, and hose. When the car was getting warm it would lose power almost completely leaving us stranded a couple of times. Let it sit and cool off and we could drive it for a short period of time again. It was losing fuel pressure. In the end it turned out to be that we forgot to fill up the coolant after the intake swap so the temp sensor was getting some nasty info that had seriously negative affects on the car. Anyway that's been remedied and the car is running great, however we're left with this raw gas smell that we can't find the source of. Hopefully that gives you a little insight into our history and might help you to lead me in the right direction.

Before everyone burns me up about using the search feature, I promise you that was the first thing I did. I used several posts to help me search through and check the connections at fuel pump, tank, expansion tank, filter, fuel rail and everything in between. All connections are tight, no hoses are ripped or failing, and there's no evidence of any gas leaking anywhere. So why is there such a crucial raw gas smell while driving? It only happens when the car is driving and typically at decelleration. Doesn't have to be after a hard accelleration, but take your foot off the gas and the cabin becomes full of fuel smell. I can't smell it at any other time. I can't get the car to recreate the smell by revving it while sitting in the driveway. Any ideas what I should look at or how to make it happen while not driving so I can try to identify the source of the smell? This is a suddenly new issue that we hadn't ever experienced through the many years of owning the car. Exhaust smell has been an issue, but whatever, it's an old car. However the fuel smell is so strong there's no way to ignore it.

UPDATE: Sooooo..... you guys (and gals) are going to love this! :-) We finally gave up on trying to figure out the issue and we had a mechanic that we've had some history with, pick up the car and try to help us figure out the problem. Long story short, the mechanic noticed that the coolant level was really low (we lost a bunch doing the intake swap and other misc tasks). He filled that up, checked the calibrations on the AFM and TPS and a few other things..... car has run perfectly since. He's had the car for a week, letting it sit running to get hot, took it very several rides and never had one problem. Apparently the temp sensor was throwing some ugly info back the ecu since the coolant level was so low and once hot it had big time negative affects on fuel supply. He does believe the gauge we have on the rail is off as it's still only showing 20 psi, but I think he did put the gauge right after the fuel filter and was at 30 psi or more. 4 weeks of BS for low coolant level. Pretty amazing!

FastWoman: Thank you for the response and detailed instructions. I wanted to reiterate a few things from previous updates that you might have missed based on some of the comments in your last message. The fuel pump has been replaced with an aftermarket style, smaller/thinner not the fat OE style. That didn't change the flow rate at the fuel rail mounted gauge. I did remove the fuel filter and attached a gauge to the hardline coming from the pump and was just over 40psi. It wasn't a fully sealed connection at the gauge so the pressure may have been higher, but I thought that range was adequate. I also tested the AFM flap by turning the ignition on and holding the flap down. I could hear the pump immediately kick on and the gauge on the fuel rail read 36psi. That's the only time that gauge has ever read that high. doesn't that prove that the pump is working, the FPR is working, and the system can reach the correct psi? The only thing I haven't done yet is put the gauge between the fuel filter and the rail. I can do that and direct wire the pump to see what I get. I also have a question about the return line. Can you explain why I would run the test hose from the end of the FPR to the filler neck of the tank when the return line of the fuel system accomplishes the same thing? Is it just so that you can see the rate of flow coming out of the hose itself? Just trying to understand as much as I can about these tests as I do them. Thanks, everyone, for your responses.

I wanted to give a little update and get some details on how to go about the direct 12v power to the pump test. We replaced the coolant temp sensor, but still ended up with the same results so that rules it out has a possible problem. I wanted to try the direct power to the pump test to see if I can get the car running and remove the relays and other electrics that have a hand in the running of the pump. But I was wondering if you might be able to provide some details on how to do that. I'm assuming that I remove the stock power wires from the pump and then connect power directly from the battery? Once I connect the power to the pump, won't the pump be running and circulating fuel through the system? Do I then start the car as normal? Driving it in this manner is ok? Thanks.

This past weekend I pulled up the EFI Bible and the service manual and started doing some testing. In the troubleshooting section of the bible I found something that said lack of power when accellerating or something like that. It gave some parts to test and then a list of circuits to test at the Ecu connection. All went well until I got to the temp sensor circuit. We actually have a new one of them so we tried to pull out the old. Damn that thing was rust welded in place. I finally got it out but not before cracking the housing and then even after getting it out we couldn't get the nut off the sensor. So I had to order a new nut and used housing. I'll give another update after I get those and get a chance to install them. I did text the dual relay per the service manual and it checked out ok. Although I know that is while it's cold. My thought process behind moving on to the other testing is that even when it is cold and is running "better" it's still not right. I'm only getting 26 psi at most and as it warms up it drops down to 20. So there's still some issue present even when not completely running like arse. I'll update as soon as I can. With the holiday and waiting on parts I'm not sure when I'll be able to work on it. Thanks all.

Do you have any info regarding the fuel injection relay and the location of the fuel pump relay? Are they one in the same or is there a separate fuel pump relay in the car? I looked under the passenger seat and there is a relay there, but its not even plugged into anything so I have no clue what that is. I didn't see anything in the passenger footwell and all I saw in the driver's footwell is the fuel injector relay.

When you say to hard wire the pump directly to the battery do you then mean to attempt to drive the car that way and see if I have the same problem? If the pump is hard wired to the battery then it's not using any of the sensors and/or relays throughout the system to get it's power, is that correct?

Zed, Thanks for the response. Just a quick note of reply to your message. When the car was running poorly at the gas station the pressure went as low as 10-15 on the rail guage. After sitting at only idle for a while it raised back up to 20. I do have the T as well so I can put the alternate gauge in line between the filter and the rail. Do you have any comments on the rail gauge reaching 36psi when the pump was running by opening the flap on the AFM?

Just to add to a little more of my previous update. We just drove up to the gas station where we left the Z several hours ago. It started right up and we drove it home with no issues at all. We didn't leave it running long enough to heat up and start behaving poorly, but do you think that confirms it's an electrical issue with the fuel system and not something mechanical? One more thing I'd like to note. I pulled the AFM just to check the flap and make sure there isn't any issues with that. All seems well. We also checked to make sure the pump would come on with the key in the ON position and pushing the flap open. The pump fired right up, but... here's the funny part. The gauge on the rail immediately showed 36psi. That's the first time that's every shown that high of fuel pressure. So what does that tell us?

Ok. So I have some new information to share. I'm still stuck and the car is still acting up, but here's what we've done. I got some additional hose, the Lowes gauge and some direct nipples to try the gauge in different areas of the system. I pulled the fuel filter and stuck the gauge into the fuel line come straight off the pump. Cranked the engine a few times and it show up over 40 psi. I got the same thing after the fuel filter. We started the car up and it was running fine. We let it sit for a while a warm up. Continually checking the car's ability to rev without any breaking up. It continued to do this without any issues so we decided to take the care for a ride. BTW the gauge on the rail was reading about 26psi when it first started and eventually got down to 20psi before we took off to test drive. I didn't worry about that anymore because I think it's clear that it's not longer accurate. We drove about a mile up the road and all was good. We decided to drive to the gas station to get som fuel because we were low. That's about 8 miles away. We pull into the gas station, put the car in reverse to back up to the pump and that was the end of it running well. It immediately started breaking up if you gave it any throttle. We couldn't get the car to move under power. We had to push it off to the side. The car continued to idle just fine, but would not take any throttle increase. Someone happened to stop and asked us if we needed some help and he claimed to work for a mechanic shop that specializes in muscle cars and older cars. He asked some questions and after our description of what had been happening he suggested that the fuel pump relay could be failing when it gets hot. This would explain why it behaves poorly when hot, but it you let it cool off it will run well again and then become poor running when hot again. Could this be possible? The electrical aspect of things is where I lack experience. I've tried doing some searching online for where the fuel pump relay is located on the 77 and I'm coming up with tons of contradicting information. The EFI Bible states that the fuel injection relay is a two part relay. First part is the Power Relay and the second part is Fuel Pump Relay. I found that part in the driver's foot well above the ECU. There is one mounted in the factory location with nothing connected to it, and there is another one that is connected and stuff up above. So it's been replaced before and it looks like the previous owner couldn't get to the screws to remove the old one. However here's where it gets really confusing. The Black Dragon parts book lists the Relay-Fuel Pump as a single relay, not this much larger double relay. So I'm lost as to what exactly I should be looking at or testing. Can anyone shed any light on the electrical aspect of this? If the fuel injection relay (larger double relay) is the only relay or if there is another single unit and where that might be?

Is that gauge from lowes an adequate replacement for the fuel rail? i want to try to find something locally so I don't have to go through the whole process of ordering it online and waiting for it to arrive. Or does anyone know of another gauge from Advanced, Auto Zone or something like that more suitable for a fuel application?

So.... The nightmare continues. Before I could pick up the hose and additional gauge my dad had ordered a new fuel pump along with a few other things that we needed. So I put off purchasing the hose and gauge and we just went ahead and installed the new pump. Unfortunately the results were identical. Mediately upon starting the car the gauge on the rail was only showing 22 psi. I left the car running for quite a while to see how the car would run and what the gauge might show. It eventually got down to about 18 psi while at idle. Removing the vacuum from the FPR produced at most 30 psi. One thing that was a little odd was that the car didn't seem to break up like it was previously. I didn't drive it but I was able to make it break up just applying throttle while I'm neutral. So I'm going to pick up that gauge from Loews that you listed in previous post and I'll apply it before the filter. Should I do that in the dead head layout or just put it online with the T fitting that I can screw the gauge into? Also what should I be looking for? If I put the gauge before the filter it should read close to 50 psi? What if I'm not getting that? What should I check then?

I happen to have another new fuel filter so my dad is going to through that on today and see if there's any change in how it's running. I haven't had a chance to do the test in Post #5 as it was a holiday weekend back then and wasn't able to purchase the additional items needed at that time. I'm going to gather everything up this week and plan to do that next weekend. The car resides at my dads house in Md and I'm in Va so I don't get any time during the week to mess with it. I'll report back my findings after I run the test on the pump and I'll pick up an extra gauge that I can try to run inline before the filter as well. Thanks All.

All: We finally got around to receiving and replacing the FPR today, but we still have the same results. The car starts out fine, but once it warms up the pressure drops off and applying any throttle causes the idle to break up. So we've eliminated the FPR as the culprit, what should I be looking at now? Is there still potential for the pump to be the issue? It just seems strange for the pump to be working just fine before we removed a single part from the car and then immediately upon completing the intake swap, the pump is no good. I feel like there has to be something else I should be looking at, but at this point I'm lost. Any suggestions?

It is new, but then again, so is the fuel pressure regulator, so that isn't saying much!

Zed, Thanks. I have done that test already and I can tell you that it never gets more than 30 psi pressure no matter what I do. I'll have my dad order another fuel pressure regulator and we'll give that a shot. I picked up the one I got recently from a local advance auto. Any recommendations on purchasing locally or ordering online from more reliable Z parts source?

Fast, I'm not sure I follow why the check valve a your suggestion on the defective part. If you say this part affects hot restarts and not the running of engine, why would it be a potential problem? The car doesn't have a problem starting cold or hot. The car does have a big time problem of not having enough fuel after the car warms up. I was thinking, and you guys correct me if this sounds absurd, but if the car isn't building up enough fuel pressure while running AND drops down to zero immediately after shutting off the car would it make sense for one of the new injectors to be faulty? Could one of the injectors always be wide open? Never allowing pressure to build and eliminating all pressure as soon as the engine shuts off? How can I test that? Aside from reinstalling all the old injectors, I'd rather rule out certain parts instead of guessing. Be the way I did try punching off the return fuel line even when the car has warmed up and is only getting 20-22 psi. The pressure would rise to over 40 psi when pinched. I couldn't complete the test of running the pump with the return line extended to the fuel tank filler tube because none of the part stores are open to get more hose.

Thanks Fast. I will give this a shot today and see what results I get. I know I can recreate the hot running low fuel pressure in my driveway but that's with the car running. I'll need to head to the store for some fuel line to go from the engine to the fuel tank because I don't have enough line left over now. One thing I forgot to mention in my original post was that when I shut the car off the fuel gauge goes immediately to zero. It's not holding any pressure. It used to hold pressure before. It would reduce over time, the car isn't a daily driver, but it always held something. Yesterday after driving it, I shut the car off and pulled the hose off the filter and had no pressure. Does that make any difference in what the issue might be or does that still point at the pump as the potential issue? I'll post results later today. Thanks all.

Zed: Thanks for the response. I did not purchase an adjustable FPR, I just purchased a replacement stock model. I started the car up just now and had about 30 PSI (that's where the pressure is when cool) and then pinched the return line and the pressure shot u to over 40 psi. So what does that mean? Is the FPR not working correctly? Does this rule out the pump as a problem?

Hello All: My father and I have own several Z's over the years, but we've had this 77 280Z for quite a while now. I've collecting some parts to lately to do a "intake clean up" project. I found a non-egr intake manifold and purchased a PALNET fuel rail. New injectors, o-rings, fuel filter, fuel pressure regulator, pvc valve, fuel hose and vacuum hose. We just completed all of the work and at initial start up the car was running fine. Fuel Pressure was a little low but seemed to idle fine and rev smooth. We took the car for a fine and about 2 miles down the road things went way down hill. Any throttle caused the power to break up horribly. Car would idle ok (fuel pressure gauge only reading 20 psi) but any power would totally screw it up. We had to limp it back to the house, but it was blowing blue smoke from the exhaust. When I popped the hood i found see some fuel around one of the jnjectors so I pulled that one and replaced it with one of the old ones, buttoned it back up and tried again. Again it started right up and would idle fine and rev smoothly. We let the car run for a while for it to warm up and eventually the fuel pressure dropped and any throttle would cause it to break up. While cleaning up the intake I removed the CSV, AAR and disconnected the Thermo Time Sensor. I removed the magnet valves and air tank associated with the AC. I did keep the charcoal canister in place and connected as it should be. Just to be clear the car was running just fine before doing this so there weren't any issues that I was hoping to correct while doing the intake clean up project. https://db.tt/SyCkTvNx The link above will show you some photos that I took of the engine compartment and 3 videos that I took with the car running. I'll give you a summary of each below: 1st photo - fuel filter side of the engine compartment 2nd photo - fuel gauge showing 30 psi at initial startup 3rd photo - intake manifold side of the engine compartment 1st video - initial start up, you can see that no throttle change the fuel pressure 2nd video - engine idling w/about 30 psi of fuel with vacuum removed from FPR, you can see the change when I reconnect the vacuum, it drops to 20 PSI 3rd video - the car is warmed up enough that any throttle total bogs the motor down I've done quite a bit of searching but thought it was time to create my own post and see what kind of responses I get. Any help or direction on what to check would be greatly appreciated. Patrick