My car is hard starting, especially when cold, but seems to run fine a minute or so after I get it started.

The other day I was going to do some work on a fuel line and when I went to depressurize the system, there wan't any pressure.

Does it sound like my fuel pressure regulator could be bad allowing fuel to too easily run back to the gas tank and not maintaining pressure in the system?

I don't know where else the pressure would be "leaking" to since I don't smell gas or see any actual leaks.

Thanks

Gary

Just sounds like you don't have a properly functioning cold enrichment (choke) system. The simple fact that it runs better after its warm fits that diagnosis. You have SU's on that beast, don't you? If not, let us know what type of fuel system you have.

To check fuel pressure, just put a gauge in the line after the reg and before the carbs and see what its doing during startup and while running. Carb systems don't typically keep much in the way of pressure, but rely on what's in the float bowl to get you started, then by the time that's used up, the pump should be adding fuel to the bowls if there wasn't any residual pressure.

Let us know what you find

You should really put the year of your car in your posts or signature. A 76 280Z would maintain pressure in the lines. Unless the original poster (or previous owner) changed the fuel system, the car does not have carburetors.

The problem could be a fuel pressure regulator. Download a copy of the FSM and look in the EF section for troubleshooting tips. Also consider getting an inline gauge and installing that to see what the fuel pressure is while the engine is running and after you turn in off.

You posted a little while ago that you were planning to replace your injectors, no?

Replace the cold start valve (injector) while you're at it and your cold start problems should go away.

There's no point checking fuel pressure with a handful of 30 year old drippy injectors. You already know they're leaking.

And I'm going to arse--U & ME you've already read all the threads about re-habbing your Auxiliary Air Regulator, AAR...which ALSO needs to be working properly for a smooth warm-up.

Edited October 4, 201212 yr by Wade Nelson

First, sorry guys for not mentioning this is on a 76 FI, that's usually the first thing I mention when I post.

Yes I did recently replace all the fuel injectors and yesterday I did order a new cold start valve in case it was leaking or not opening properly. I also ordered a new theromotime switch. I do have a FSM which tells how to test some of this stuff, but since the car is almost 37 years old and I do plan on keeping it, I figure I might as well replace that stuff sooner than later so I can get it running as good as possible and enjoy it.

I also cleaned-up the electrical connector on the aux air regulator and that did seem to help some. For example, when I start it from cold, I now get that little "bump" in RPMs to about 1,200 before it settle back down to idle at around 800 RPM. I'm now in the process of cleaning many of the other electrical connectors.

So at this point I'm not sure if I should pull the Fuel pressure regulator and bother testing it or considering its 37 years old, just replace it for the $60 thinking that might help maintain pressure in the fuel system.

Thanks

Gary

I'd get a gauge on the fuel line too, temporary would do fine for testing. I bought one off ebay for $15, 0psi to 60psi. $5 more for the "T" from auto parts store. At least you won't get sprayed with fuel when your taking off the lines. Smiley face goes here.

Just did my '04 Tahoe which had the same issue. It was the pressure regulator which was odd because it held a vacuum and wasn't leaking externally. Must have been the O-Ring on the high pressure side which would leak to the low pressure return line; low pressure O-Ring problem causes an external leak as would the diaphragm cracking). Figured it was the regulator or a leaky injector. Found a whole set of injectors for the truck for 150.00 which blew my mind http://www.fuelinjectionsurplus.com/NEW-OEM-FLEX-FUEL-FJ502/dp/B000IYLJFS?field_availability=-1&field_browse=5436368011&field_product_site_launch_date_utc=-1y&id=NEW+OEM+FLEX+FUEL+FJ502&ie=UTF8&refinementHistory=brandtextbin%2Csubjectbin%2Ccolor_map%2Cprice%2Csize_name&searchNodeID=5436368011&searchPage=2&searchRank=salesrank&searchSize=12

Why would you order a replacement $60 Fuel pressure regulator (+ shipping) instead of "Teeing" a gauge into the fuel line, sucking on the vacuum line on the FPR and seeing whether you NEED a new one first? Do you prefer hanging parts to doing diagnostic work???

Checking your fuel pressure could ALSO help you identify a leaking check valve back at the pump or other issues.

Wade, good point. I have done alot of diagnostic checking on the car with my ohm meter (eg, the AFM checked out OK for each test) and adjustments such as valve lash, etc. But since this car is almost 40 years old, what might check out OK today, will probably need to be replace anyway in another couple of years. And some of the tests require purchasing extra tools such as a fuel line pressure gauge or cumbersome procedures like heating the thermo-time switch in a water bath and checking the change in ohms as the temp changes, etc. I figure the pressure regulator has probably taken a beating from heat over the past 37+ years considering it sits right above the exahust manifold in the center of the engine. Spending $60 or so bucks doesn't seem too bad to quickly solve a problem, if that was the problem, however, if I suspect something like the fuel pump which may cost me $200, I'll definately try performing some testing first.

I guess when I post regarding an issue, I always hope someone else who might have had the same issue replies with, "I had the same problem and it was my ....." This is a great forum.

But you do have a valid point about testing vs just replacing. As I mentioned, I do plan on keeping this car. I've had a lot of awesome cars like a 62 Austin Healey 3000, a 67 Camaro, etc. But this is really a cool little car and will by my cruiser when my wife and I retire in a couple of years and I'm not pulling that blankety blank 5th wheel trailer she likes so much. Gary

You make good sense Healy Man. $20 gauge makes that new FPR $80 instead of $60. I got mine from rockauto.com