78' 280Z stumbles under throttle application

[Virto]

I'll give it a shot when I get home - honestly I was kind of hoping you'd chime in. If it is in fact a lean condition, I would blame either the pump or the pump screen initially, given the pump's cry for help.

I won't be able to get the pump pulled until this weekend, at the earliest.

How many different sizes of fuel hose did Nissan use on these things? I was hoping the FSM or EFI bible would list hose sizes in specific locations - It'd be cheaper to buy a spool of hose and replace things as I go than to buy cuts from the parts store. I noticed my upper hose from the filter to the fuel rail is cracking - spurring my desire to replace the old rubber.

I'll report back on the FPR in a few hours.

[Virto]

OK, pulled the vac line off of the FPR and opened it up - no backfire.

Reconnected the FPR - no backfire.

Decided I'd better have an idea of what's going on, so I climbed into the cabin. I was able to rev it freely from idle to around 5k. I wasn't about to push it more than that parked in the garage. It did stumble again a couple of times when it was around that 5k mark.

The pump is still loud and the fuel filter bracket is going to have to come off - I still can't turn that screw. The screw head is too soft and the slots are too shallow to get screwdriver to bite.

So I've essentially eliminated nothing here, in my search for the issue. My budget is shot for the month, but I need to get my hands on a fuel pressure and a vac gauge, I expect.

[Wade Nelson]

add a little clear Fram between the tank and pump"

Nope, those are for carbureted applications, 1-3 psi.

Those are NOT designed for fuel injection pressures! Filters for fuel injected vehicles are almost invariably METAL CANS that can survive 20-50psi.

[Virto]

Nope, those are for carbureted applications, 1-3 psi.

Those are NOT designed for fuel injection pressures! Filters for fuel injected vehicles are almost invariably METAL CANS that can survive 20-50psi.

Honestly, I hadn't even considered that possibility. I was just following the write-up over at Z Car Tech Tips Fram G3 Filter Installation

The car in the example is a 77...but maybe it's just luck that nothing has gone wrong?

[siteunseen]

The high pressure is after the pump. Go ahead and put the G3 between the tank and the pump.

[FastWoman]

I agree. I have a low pressure filter on the intake of my pump as well. No problems so far. The next time I replace it, I might use a clear, polycarbonate filter, so that I can see any debris. Something like this:

Spectre/Clearview replaceable fuel filter (6932) | Performance Fuel Filter | AutoZone.com

I installed that filter on our 318 inboard boat (which would suck down fuel like a Russian sailor would swill vodka) and had no starvation issues. It's not a particularly fine filter (speaking in terms of particulate size), but it would catch any larger junk that would do damage to the pump, and it should be pretty free-flowing. I've also used this same filter for many years on my tractor.

Your pump noise MIGHT be due to a missing or malfunctioning fuel damper. The purpose of the damper is to reduce fuel pump noise. Also check that your pump is supported with rubber and is not mounted metal-to-metal. Ordinarily the pump makes a tiny whine. You can hear it, but not very easily.

The random nature of the stumbling suggests to me that you might have dirt in the fuel rail / injectors. Of course it wouldn't distribute itself uniformly if that's the case. How do your plugs read? Do they all look the same? Different?

Hose sizes: The two supply sizes are 5/16" and 3/8". (OK, those aren't metric sizes, but they're close enough.) As I recall, it's 3/8 from the tank to the pump and then 5/16 thereafter, but you'll want to confirm that before buying hose. If you end up getting into the bigger project of replacing your fuel vent lines, then you've got some bigger sizes there. I believe the biggest is 5/8". Resist the temptation to buy heater hose. You'll need fuel-rated hose. You can get that size of fuel hose from a tractor supply and also from Hampton Rubber in Hampton, VA. (You'll have to call them and put together an order.)

Your stubborn screw: DON'T DO THIS IF YOU HAVE ANY FUEL IN THE AREA: You can always use a dremel tool to make a slot that a flat-blade screwdriver might like. Use a low speed, and don't make sparks. Take your time. If the screw still won't turn, maybe you can cut off the head, remove the part, and turn the screw shank out with some tiny (and new/sharp) vice grips.

I've gotten in the habit of replacing all of my screws with stainless, by attrition. I think I ordered some stainless metric assortments from BoltDepot.com -- like this one:

Metric assortments, Small plastic compartment boxes, Metric Bolt Assortments, Stainless steel, Metric hex bolts (coarse thread) w/ nuts, flat washers, and lock washers 6mm - 10mm - Bolt Depot

Also buy some antiseize lubricant. You'll want the nickel variety for putting stainless into aluminum, and any variety will work for stainless into steel. Be careful, though, because a well lubricated stainless screw can back out.

[Virto]

I'll install an in-line filter for sure, whether I swap the pump or not. I'm anxious to look at the pump screen and see if it's all plugged up. Five bucks for a little added protection never hurt anyone.

Plugs all looked the same when I replaced them prior to waking the car back up. I haven't pulled them again, but it's only run maybe 6 times since the install. Pretty sure they're BPR5ES-11, which might be a little hotter than I need but for now they'll do OK. The old plugs were pretty nasty, but they weren't oily or gas-washed, and they were all uniform in appearance and rather old.

Thanks for the sizing info. I'll give it a double-check next time I'm in the garage for the high-pressure hose and then the tank to pump and pump to damper when we get it up to check on the pump and install the in-line filter.

I thought the damper was intended to prevent any kind of surging flow from the pump, almost like a 2nd FPR. Looks like the only way to test the damper is to stick a fuel pressure gauge right after it and see if it bounces around, per the FSM.

I've considered simply punching a slot for a flat-head screwdriver with a chisel, dremel makes more sense, but I wouldn't try that unless I can push the fuel filter out of the bracket first. The screw is very soft, it should be very easy to cut. With the bracket removed, I could probably just drill it out, worst case.

Thanks for taking your time to help with this. I spend a lot of time poking through most threads on the board just to glean a little extra insight into my own issues.

-Kelly

[madkaw]

Doesn't autozone lend out fuel pressure gauges ?

You need to find out what your pressure is. High pressure would indicate a blockage which would cause leanness and a screaming fuel pump.

In my case it was a blockage in the return line of the fuel sending unit. When I got inside the tank it was very clean and the sending unit looked new, but something got sucked up in there and stayed. I was running like 75-100 psi

[Patcon]

I was doing a little parts sorting in the shop today and came across a fuel pump assembly out of a 76 280z. If it would help let me know and I will post a picture to confirm its the right item and test the pump to confirm it runs. It could be had for postage...

Charles

[FastWoman]

Kelly, you need to install a fresh set of plugs, so that you can see how the individual cylinders are running. If any of your injectors are partially clogged, the corresponding plugs will show lean, while the others show normal, less lean, rich, whatever. If you have a completely clogged injector, the plug will look brand new.

The other way you can check the health of your fuel rail is to pull it and spray fuel into little glasses with it, essentially flow-testing it. However, that's pretty labor intensive.

[Virto]

Charles - That'd be great, I'd be more than willing to pay for your trouble.

Do you think I could stand to just pull the plugs I've got now and look at those versus swapping them again? They're a month old and have maybe 7 starts/runs on them.

[FastWoman]

Oh, I misunderstood! Never mind. I thought you had the same plugs as when you put the car to bed many years ago.

So you should pull and read them now! Do you know what to look for? Can you post a photo?