Starting issues

[jewelz]

So I bought a 240z about a month ago. It has the L28E swap from an '83 280zx. The motor is fuel injected. The guy I bought it from let me know that the gas tank was never swapped, so it is still has the 240 gas tank with the 280 fuel set-up. He said this was causing a little gas starvation when mashing the gas pedal or taking hard turns.

The car ran fine the night I got it, then started up fine the next morning. As soon as I got out to the road, I went to accelerate to make a left turn but couldn't seem to get any power out of the car. I made it to the median, and the car died. After a little bit of work, I got it started back up. I had to nurse it back home then left it for the day. We changed out the spark plugs, cap and rotor. The car ran much better for a couple of days after that. I went to start the car a few days later, and now it turns over, but never catches. It just sits there kind of sputtering, sounding like it's right on the edge of turning over. I went back later and tried to start it again, thinking it just sounded like it was flooded. After a lot of coaxing I got the car to start. I let it warm up for a while, then attempted to drive it. The car wouldn't stay started unless I pumped the gas peddle quickly, then it wouldn't rev high enough to actually move until I had been pumping for a while. After some time, the car would kind of catch then would rev up high enough for me to move it, but would drop back down a little bit later and I would have to start the process again.

Now the car just won't start at all. I've been thinking it sounds like it's just not getting enough fuel to start, so I dropped the gas tank and cleaned it, but that only slightly helped. It now tries a little harder to start but still won't catch. We've put a brand new fuel pump on, rigged up the G3 filter between the tank and pump, checked the fuel pump relay, and fuel pressure regulator. Everything is turning up to be fine. I know that we're getting fuel pressure at least to the fuel rail but I'm not sure how much.

Here are my questions:

Does this even sound like a fuel issue? If so, what is the best way to test the injectors, and where should I go from here? Is there a way to check fuel pressure without the car being able to start? I'm working my way through that Z fuel injection manual, but I'd like to see if there is a smaller place for me to start to attempt to fix the issue.

Thank you!!!

Edited March 3, 2009 by jewelz

[sblake01]

Depending on how the previous owner set it up, it would either prime the fuel system when you turn the key to the on position or when you begin to crank it. Those were the only two ways Nissan actuated the fuel pump during the 10 years they used that system. One or the other would show fuel pressure if everything else was right. I'm referring to the stock EFI system which may or may not apply to yours since it's a conversion.

[jewelz]

Thank you sblake!!!

I luckily didn't even have to get that far. I had put new plugs on the car, so I didn't think about the possibility of that causing my problems. I went out and double checked the plugs though and they were fouled. I replaced them and she started up and is idling beautifully!

I really appreciate all the help you give. It's probably a good idea for me to check fuel pressure at some point anyway.

[sblake01]

Keep an eye on those new plugs. If they foul again in a short period of time you might have some sort of fuel richness or weak spark issue.

[jewelz]

Hello again...

So, I drove the car for a while the night I got it running. Things seemed like they were going pretty well, but I was still having some issues when pushing the car past about half throttle. The car was kind of "bogging" down. When I went to drive it the next night, I was experiencing the same problems as I was right before the car got bad enough I couldn't start it anymore.

I pulled the plugs again today, and they were already fouled. From what I can tell though, it seems like the plugs are getting fouled with oil. That's what it smells like at least. Is there anything specific I should be looking at now?

I'm really worried about problems with rings or something....compression test is next. I'm just curious where else to be looking.

Thank you again for all the great advice Stephen!

[sblake01]

Fouling with oil isn't a good thing. That generally means valve guides or rings. Are all 6 plugs fouling? Does the car smoke when it's running? Especially when you push it past half throttle? A compression test will help pinpoint it. Let us know what the readings are.

[jewelz]

Yes, all six plugs are fouling. It smokes a lot when pushing past half throttle. A lot of black smoke....we were worried about burning oil, but my oil level doesn't seem to be dropping at all or having issues. Of course, I haven't had the car running long enough to have a good basis for a conclusion against burning oil.

[jewelz]

So we just finished the compression test. Looks like I have all cylinders at 130 PSI. This is with the motor cold. I got her up and running today and she drove much better. I'm still having issues if I give her full throttle...she'll completely bog down at about 3k rpm that way, but has no problems accelerating steadily if I keep it at half throttle. I think the other night's issues may have had something to do with the colder weather.

I think the plugs were just wet...they smelled like gas instead of oil this time....dunno what's going on there. Diagnostics continue!

[sblake01]

Black smoke generally indicates a rich fuel mixture. This isn't an easy one to diagnose for me since it's a conversion. If the person that did the conversion swapped everything from the EFI car (except the gas tank) then normal troubleshooting would apply. If not, I'd just be guessing. The first thing I would check is the throttle position switch followed by the temperature sensor, both condition and integrity of it's connection, and then I'd check for leaking injectors/cold start valve, and the operation of the thermotime switch. Have you checked the fuel pressure?

[jewelz]

Thank you so much for the direction!

I wish I could say a little more about the swap...I'm pretty sure he just did the straight swap with everything except the gas tank. At least it appears to be 280 fuel lines and such. After market exhaust header too. I'm thinking something to do with throttle position as well. It doesn't matter what the RPM is from what I found tonight, it just has issues with full throttle.

I haven't done the fuel pressure check yet. I still need to get a fuel pressure gauge, and the car has me a bit broke at the moment. Checking that and timing will be my upcoming goals.

I really appreciate you helping me on all this!

[sekjr]

Someone may correct me if I am wrong BUT

Sounds like you are burning rich.

Which means your cold start valve is not turning off!

Thermotime switch needs attention! It controls the cold start valve. Page EF-16 of the Service Manual...