Forums/Z31P/z31-repairs-forums engine-mechanical/Three dead fuel pressure regulators means a bigger issue?
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Tomakze: (2013-07-18 08:31:46)
So, I found what was causeing my car to misfire… a bad FPR. The original one put out 40psi and never varied, like it jammed. So, I replaced it with a brand new one, and had one day of the engine running right, and then new, similar (But not the same) misfiring. I test the new FPR with a vacuum tester, and it sucks fuel out the vacuum line. I figure, no biggy, must have been a dud. Order another new one, get one day of the car running properly, and then it starts to act like it did with the first FPR. What is going on here?
All this started happening after I installed the manual tranny in the car. Could the return line have been crushed? The tranny went in smoothly, I don't recall it hitting anything at any point. Would a crushed/clogged return line even do this? Or am I just that unlucky that I'd buy two duds back to back? I NEED this car to run correctly so I can get my emissions test done before my temp tags expire. If anyone has any insight into this, I need to hear it. Is there a way I can test the flow of the return line? I plan to do a visual inspection of it tomorrow.
I should also mention, I have a Walbro fuel pump in the car. It ran great for quite a while after I installed that, so I doubt that has much to do with the problem, but it may be worth mentioning.
Careless: (2013-07-18 09:18:44)
i doubt the walbro has anything to do with it. good idea on checking the fuel lines for kinks. you could unhook them end to end and blow them out with air.
stupid question: is your fuel filter on your return or your feed? thought i'd ask for asking's sake.
i would still try one more fuel regulator. i would try an adjustable one with a liquid filled gauge.
Tomakze: (2013-07-18 17:59:33)
I'll check to make sure my return and feed lines aren't crossed, just to be safe. Where would I get an adjustable FPR like that? Do you have a suggestion for a good one? I like that idea a lot.
liladair: (2013-07-18 18:10:03)
Aeromotive makes kick ass units. They can be a little pricey though. Install isn't hard just takes a quick brainstorm on where you want to mount it
Careless: (2013-07-18 18:59:16)
aeromotive makes junk units that are overpriced for whats inside them.
weldon or fuel lab.
Tomakze: (2013-07-19 02:19:16)
Something like this?
http://cgi.ebay.com/ws/eBayISAPI.dll…tchlink:top:en
I also saw some much cheaper kits without the gauge, and they come in 6an and 10an like this:
http://www.ebay.com/itm/FUEL-LAB-FUE…3f45fd&vxp=mtr
Anyone have a picture of how this is hooked up? The stock one has two inputs, I can't tell if this one has one or two. I assume it still increases pressure in a 1:1 ratio to manifold pressure?
Tomakze: (2013-07-19 02:23:07)
Just found this:
http://www.ebay.com/itm/Adjustable-F…0fce1a&vxp=mtr
Any opinions? Seems like a good deal, and looks just like a Fuel Lab regulator.
Careless: (2013-07-19 02:37:51)
doesnt matter if it looks just like.
its what's inside that counts.
that's why the aeromotive units are a joke.
they are not constructed as well as fuel lab, fuel sx or whatever, and weldon
do they work? sure.
but for the same price you can get a better unit like the fuel lab ones.
get a real fuel lab, you don't need -10 AN lines, -6 will work fine.
make sure it's a 1:1 rising rate fuel reg.
1psi boost increase = 1psi pressure increase
Tomakze: (2013-07-19 03:40:57)
I can't seem to find where it shows the rate it rises at… I know it needs to be 1:1, but which one is??? Even Fuel Lab's website isn't terribly helpful…
liladair: (2013-07-19 04:21:01)
To each their own I've never had an issue with Aeromotive stuff
Tomakze: (2013-07-19 06:01:12)
Well, I checked the fuel lines. No visible kinks, or any damage of any kind. I do indeed have them hooked up correctly, and the line with the filter is the pressure line. I also hooked a funnel to the return line and poured fuel into it, and it drained at what I would deem an acceptable rate. Looks like my fuel system is fine, and I actually bought two bad regulators!
I still would like to know which Fuel Lab unit to buy. Their "mini" fuel pressure regulators look pretty trick.
Tomakze: (2013-07-19 06:05:23)
I like this one:
http://www.ebay.com/itm/FUELAB-53501…e0f0b2&vxp=mtr
Will that work?
G-E: (2013-07-19 06:27:11)
What about AEM? http://www.ebay.com/itm/AEM-25-302BK…bc7b95&vxp=mtr
GuerreroZ: (2013-07-19 13:07:21)
hey Tomakze, it seems that i been having the same problem you been having, and i also replaced the damn fpr, it ran good for a while but now its going to crap, besides what ever else is wrong with my car, but here is what i did yesterday i replace that relay by the battery the blue one and seem to helped it alot, now here is the thing even though it helped, it was still shaky, and as soon as i remove that vacuum line out of the fpr, the engine smoths out,(also if i have the vacuum line hooked up to the fpr, besides been shaky, if step on it it just dies, plus misfire, it seems like to much air is going and not enough fuel) But like i said as soon as i take that vacuum line, it works much better, it smoothes out and if i open the throttle body it revs up almost normally, so i assume the fpr is bad, now i checked the fuel line going into the fuel rail, by disconnecting it and hooking up a gauge to it, it read 60psi but i assume that is cuase i dont have a Tee to see the actual pressure going into the system, now i have a question for anyone that help, how can i make sure my fpr is not the problem, by what i just said i believe it is, so just go ahead and replace it with a stock one or buy one like the ones you guys are metioning? Sorry for the grammar errors and for the long write up, and thanks for the help
Tomakze: (2013-07-19 17:00:45)
That looks nice. Do you have any experience with it? I like the price.
I still don't know if it is a 1:1 rising rate FPR… How do I find out? Or are they all 1:1, so they don't bother listing it? Seems like an important stat to leave out of the description.
Tomakze: (2013-07-19 21:08:42)
Okay! I called Fuel Lab, and they have great customer service. All the regulators are 1:1 rising rate, or at least all the MINI series are. I guess I need the 53501. I'm pulling the trigger on this. It's roughly the same size as the stock unit, so I'm hoping I can find a way to mount it in the stock location. I really like the look of the fuel lab, and the size is great. I also love that it has a port on the front for a pressure gauge… no more bleeding the system and installing a pressure tester! Hopefully this is a permanent fix, and will be a good investment later on when I build the VG33 I hope to put in! Thanks for all the help, guys!
Careless: (2013-07-20 02:04:18)
you're going to have trouble mounting that in the same location and getting the lines to fit perfect. the stock reg has lines that curve towards the regulator on an angle. i had to mount my and fabricate some 3/8 brake line with bubble flare fittings to re route my fuel pressure regulator to where the EGR was.
Tomakze: (2013-07-20 06:13:27)
Damn. That's a pretty engine! I'll look at it and see what I can do to make it fit. The hard part right now is figuring out what gauge to use!
Tomakze: (2013-07-20 06:24:55)
I went with a dry gauge. The oil filled gauges change pressure based on temperature. The dry ones stay accurate, but sometimes fail due to vibration… It was inexpensive enough, if it does I will switch.
Careless: (2013-07-20 06:38:17)
thanks. years of fuel leaks from not having the proper upper intake to make the change over to my dedicated fuel rails were not kind to the motor. it runs great, but it the valve covers look poo.
Tomakze: (2013-07-20 07:11:47)
I'm not sure I've ever seen your build thread… That just occurred to me.
I just realized the new FPR will change more than the old location… I assume I no longer use the fuel temperature sender and the solenoid? I may find a way to leave the sender attached, just so the ECU doesn't report that as a code. That, or maybe install the appropriate value resistor on that wire. Not that it matters much, I just don't like useless codes. I'm OCD about weird things that shouldn't matter.
Careless: (2013-07-20 08:31:43)
pretty sure you've never seen my build thread. i don't have one.
the fuel temp sender only works to open the surge tank pressure to give the fuel pressure regulator pressure when you're trying to start up. you can mount the fuel temp sender two ways. get a T fitting for your gauge and put a plug into the T port, then drill and tap it to the same thread as the Fuel Temp Sensor.
And reroute your vac lines so that everything remains the same, it will still work exactly like stock.
Tomakze: (2013-07-20 18:40:35)
That would explain why I haven't seen it then!
I was under the impression that the '85T didn't have a surge tank… I am also running an '84T ECU.
Careless: (2013-07-20 18:44:58)
it doesn't have a surge tank. I'm not sure how the Fuel Pressure Solenoid works on the 85's. I don't have one.
But either way, you could just reroute the vacuum lines with some silicone line so its nice and shiney and black and whatnot rather than dark grey and old lookin' as soon as you take it out of the package.
Tomakze: (2013-07-20 21:14:35)
I already have a ton of silicone line laying around, so I will definitely do that!
Tomakze: (2013-07-21 17:26:07)
I went ahead and bought a z32 fuel filter as well. All new rubber lines, filter, regulator, gauge, etc will be going in soon. Hopefully that will finally be it with the fuel system for now, until I can afford to tear it apart and replace/clean the injectors.
Tomakze: (2013-07-30 21:56:58)
I'm struggling to get the fuel pressure set correctly. I read a NICO forum post for a 240sx, and they suggested using a jumper on the fuel pump relay to activate the pump and keep it running with the engine off, so the fuel pressure could be set more precisely. (Since the pressure will be more consistent without the injectors releasing.) Should the pressure still be set to 37psi? (Since there will be no vacuum).
I ask, because the car still runs poorly. Set to 30psi at idle, it misfires and has no power on boost. If I turn it up to around 35psi at idle, it runs much better, but still somewhat down on power, and misfires. Today I am going to revisit all the settings on my car (TPS, FPR, idle, etc.) and pull the cat to see if that is plugged. I just can't shake the feeling that there is another problem.
G-E: (2013-07-30 21:58:56)
Unless your regulator is retarded, or your pump dying, it should have no trouble adjusting to a given pressure with or without injectors… don't overthink this
Tomakze: (2013-07-31 05:19:25)
Fair enough. I think I solved most of the issue today… The new FPR had a vacuum leak. A little teflon tape on the adjustment screw fixed it though, and I re-adjusted everything. Set timing, set fuel pressure, tested the TPS, checked for vacuum leaks, and more. For some reason, the car runs much better with the FPR adjusted with higher pressure than the FSM calls for. It says it should have 30psi at idle, and the car runs much better with about 33-35. Either my pressure gauge is inaccurate, or I'm compensating for something else.
I also tried to adjust idle, but the idle adjustment screw didn't do much. I don't know how much you should have to spin it to make a big difference, but it took about two turns to get maybe 150RPM out of it. Maybe that is a clue to another issue… I did spray brake cleaner around it to see if there was a vacuum leak, but it didn't seem to affect it.
The car runs much better, and is pretty drivable now, but still far from perfect. It doesn't like it when i engine brake (Sometimes it will stall, most of the time it will chug badly and won't accelerate for a few seconds.) To demonstrate this, and to hopefully enlist more help in fixing this, I took a couple videos.
Hopefully this will help!!!
[archived image: th_CAM00182_zpsf6f2013c.jpg]
[archived image: th_CAM00183_zps8a158c95.jpg]
Careless: (2013-07-31 05:41:54)
you might just have an injector that isn't spraying as much fuel as it used to due to clogged mini-filter at the injector inlet or just general shittyness with the coil itself, so maybe thats why increased pressure brings joy.
Tomakze: (2013-07-31 05:53:25)
Considering the car sat for 15 years, and had a super rusty tank originally, this thought had crossed my mind. I ran a shit ton of injector cleaner through it, and all seemed well for a long time. I'm now wondering if this problem had existed the whole time I've owned the car, but since it had an automatic tranny, it was less pronounced. Even with the autofail, I had noticed it would sometimes seem to accelerate harder than others. I thought the tranny was slipping. I suppose I should disassemble the intake and send the injectors in to be cleaned and bench tested somewhere. I'd guess they are very expensive to replace.
Careless: (2013-07-31 05:55:30)
you can make a home made injector tester. BLOZUP had a thread here, and there are some videos online. you can also get used injectors that work rather than fork out money to have them cleaned or replaced.
if i had been working on my motor to install the bigger injectors i would sell you mine for next to nothing but im working on "something else" right now, so the injectors will stay on the motor for a while longer.
G-E: (2013-07-31 06:35:32)
I had a '98 3.0L extended caravan for a while that was beat to hell and kept working, my mother had the same era (97) caravan but short body…
Hers had a slight miss for well over a year, it was throwing a code, but so slight you'd miss where it came from with a stethoscope, until one day it became a full no-start condition… ended up dropping the tank to replace the filter as pressure was low, only to find out the mesh on the pump had glazed over and wasn't letting it suck fluid
With a new pump installed, new screen, filter, everything was fine, but now there was a clear miss we could narrow down, turned out injector #2 and rarely #4 weren't doing their duty… I figured I might as well grab a whole rail and injectors from the wrecker,
New injectors in hand, passed visual test and battery click tests, I went to swap them… that's when I found out mom's van, with the plastic gas tank, had somehow managed to fill ALL the injectors and much of the rails, with what I can only describe as rust stew
I popped each injector out, dunked them in varsol, and you could see a rusty red ooze come out of each one… to this day I have no idea how it even ran at all
Tomakze: (2013-07-31 06:45:59)
I can't seem to find that thread BLOWZUP made, but I haven't finished looking. I think you guys are right, and I just need to quit beating around the bush and rebuild the injectors. When I pulled the fuel filter, red rusty gas came out in spades. I replaced the tank, but not the filler neck, I only wire brushed as much as I could reach, and I'm sure there is more rust in there. I've replaced the filter a couple more times since, and while it was never as rusty as the first time, it was still reddish colored gas. I may buy a new filler neck, pull the tank again and clean it again, then address the injectors. God damn this car has been a pain in the ass. Never again!
Augustus Maximus: (2013-07-31 07:39:38)
Check the hose to the fuel pump. Mine had a hole in it. Made me age trying to find out why the car was acting like a total POS.
Augustus Maximus: (2013-07-31 08:10:46)
Furthermore common sense tells me the regulator is there to ensure correct fuel pressure while engine is running....while it's running, get it? There is a lot of shithead info on the internet…be careful of it.
Careless: (2013-07-31 12:08:18)
it took 25 years to get that way. chances are it will take at least another 20 to get that way again once you fix it. rerax breaux. you'll get her right n purdy.
are you SURE this is a fuel issue? have you tried looking around the engine bay in pitch-black darkness with the engine running to look for jumping spark or something?
Tomakze: (2013-08-02 05:19:07)
Well, the filler neck was rusty as shit. I wire brushed it out as best as I could, but it still has rust in places I couldn't reach. The tank itself is as good as new, but rust flakes can get in it from the filler neck. Any rust that is left is small, thankfully. All the large flakes are gone, it's just enough to discolor the fuel before the filter.
I checked for jumping spark, and found none. I've seen that before, from my Datsun. Like a flashing blue light. My engine is completely dark when running. While I was there though, I remembered something… my injectors have always been kinda noisy. I dunno if that is normal or not, but there is a distinct ticking sound coming from them. (I know all injectors tick, I just mean it seems louder than an average car.) So, I took a video of it running really rough after a cold start today. Cold starts are by FAR the worst. I have to start it several times before it will stay running. I started the video right as I got it to idle and not stall. The vacuum gauge is in clear view, so you can watch it's behavior and see if it is normal. I also posted this on my build thread, so sorry about any redundancy:
[archived image: th_CAM00185_zpsaec44f14.jpg]
Tomakze: (2013-08-02 05:23:24)
And before anyone asks, the clunking sound is coming from trashed rear subframe bushings, not backfiring. I have nearly a full poly set for the car, as well as new springs and Illumina shocks waiting for me to get around to. The engine is first though.
Tomakze: (2013-08-07 23:06:29)
Not the distributor. I swapped in my brother's distributor from his perfect running slicktop, and had the same problem. The car runs way better with the adjustable FPR set way high, but then it stalls when I decelerate. I'm guessing this means my injectors are plugged. With high enough pressure, they spray well enough to run the car, but it gets too rich when I decelerate.
Either that, or I have two bad ECUs, since they both act the same way. This is driving me crazy. I just want my car to work. I guess I'll buy new injectors and gaskets for the intake. Might as well do the spark plugs again, while it's easy. Anyone know if I can run '87T injectors in my '85? (I have two different ways to get 87T injectors, lol!) I already know the impedance is fine, but I feel like I read somewhere that I'd need to modify the intake plenum since the rail is different. Anyone know?
Careless: (2013-08-08 02:54:14)
ok, well since you have to replace your injectors anyways… what i would do is buy 2 or 3 injectors from people on here. dont buy the whole lot. i mean it's still cheap- you can get them for like 60 bucks, but anyways, by a pair.
then do the following with your current injectors.
1) remove the rail, and remove each injector from the rail- label them with a number just for your own information.
2) find a spare injector connector, or buy one, or clip one from another car with some lengthy wire attached to it.
3) take the line off your fuel filter that goes to the rails, and tighten it onto ONE injector. I would recommend getting a 3 foot length of 5/16 fuel hose and shoving it onto the 3/8 line on the fuel filter outlet. it will go, but you gotta want it to go.
you don't need injection hose for testing. for normal operation it is a must, but for testing it should be ok for some time.
4) point the injector into a clear canister of sorts that is deep enough… a 1.5 litre water bottle is usually taller than a 2 litre soda bottle, but either works.
5) have someone turn the key to the on position so you hear the pump prime.
6) tap the injector connector you saved or clipped from another car very quickly to the battery on both pos and neg terminals and look at the spray pattern.
you should be able to tell instantly which one has a shitty spray pattern. start with a low PSI on your regulator to be able to tell the spray pattern even more so. take one of your replacement 2 injectors and change that one up. put all new hoses on your fuel rail, and drive the car again.
also, don't hold it on the battery for too long. i believe high resistance injectors will burn out very quickly if you don't just give it a quick 1 second pulse.
it's not a scientific way of checking flow rates and whatnot, but its better than sitting around changing parts you don't know are bunk. heck, you could even just test them before buying anything, and put it back together and label the one that's shitty and then just change that one once it comes in the mail. or you could get the injectors in the mail and just undo the filter line without touching the rest of your car, and test those ones first to get a feel for it before pulling the rest of the car apart.
that's where i would start. i think Urstin did something similar, but with the entire rail attached and sitting over the engine in a turky roasting pan so that he could test each injector one by one without removing them from the filter line- but that seems like it would make a mess. i've seen poor and spewy injectors, they squirt fuel in every possible direction. especially your face.
Tomakze: (2013-08-08 05:40:00)
Seems reasonable, thank you, Careless! I may be able to get injectors that were recently cleaned/tested for what I deem to be a very reasonable price, but they are for an 87T, as I said before. If I find out they will work, I may go that route. If not, your idea seems like a great one!
Now for the newb question… can the injectors be removed from the engine without removing the intake plenum? I didn't think they could. If they can, I may pull it apart and test them before buying new ones, using your method. If I have to pull the plenum, I'm redoing everything I can at the same time. You know, might as well.
Careless: (2013-08-08 05:42:28)
very difficult to remove the injectors without removing the plenum- I'm sure you could do it, but then putting it back in with the seals and everything would be a bitch.
you really just need to prepare with a new metal intake gasket from nissan, and 6 new injector seals, which aren't that expensive and could fix any boost leaks you miiiiiight have.
that's basically all i would buy. the rest of the stuff, just leave it on, throw the harness to the side.