L28ET HELP!!

[ZPIT U OUT]

Hey I am on my last limb here. I got a 1973 240z with an 83 l28et swap. It has a fuel cell wired to a switch. The car will run and boost really good like it's supposed to when I put new spark plugs in. After driving it about 15 min or about 20 starts and moving out my garage in the driveway, the plugs will start to foul out and miss and hesitate. The guy that did the swap told me that it was because of the fuel pump he put in out of a 98 mustang. Well I changed it for a Nissan correct lph one, and still have the problem. I've replaced a lot of parts including 02 sensor thinking that would fix it. Now Im being told it is my Fuel Pressure Reg or my Cold Start Valve. I dont have a job to go buy unnecessary parts. Has anyone experienced this problem and fixed it? HELP!! Thanks a lot!!

[RTz]

Now Im being told it is my Fuel Pressure Reg or my Cold Start Valve.

 

 

Yes, it would be wise to check your fuel pressure.

 

Yes, a cold start valve can cause excessively rich conditions. You can probably get away with deleting it altogether. My Z's start just find down to 8 deg. F.

 

It's common to have a malfunctioning water temp. sensor/circuit. Usually poor connections, but the sensors are also suspect. An improperly working water temp. sensor will flood an engine pretty quickly.

 

The AFM can also cause similar symptoms, but more challenging to diagnose. Start with the simple stuff.

 

Download the EFI Bible. It's not specific to your turbo EFI, but it's heavily related and will help you understand the concepts.

 

 

Please avoid cross posting. I'll delete the other thread.

[Tony D]

The cold start injector only functions when cranking, and an easy check as stated was 'just shut it off'---the STARTING will happen off the 'cold start enrichment' delivered through the regular injectors. All that cold start valve is used for is the initial firing off. When you crank, it's just spraying fuel into the manifold, not unlike some pit man spraying nitro down the stacks on a hilborn injected dragster. Really high-tech!

 

An easy way to check it is to unplug it. That electrically isolates it. You can also use a small clamp or vice grips and clamp off the fuel line to it depriving it of fuel source.

 

If you are still fouling out, my bet would be engine temperature sensor connection has fallen off or is loose, or dirty. That will make the engine run pig rich! In some cases wet-fouling the plugs!

 

And of course, FPR... BTW you mention a 1973 240Z and that someone else did the conversion. Your symptoms are CLASSIC for using the stock return line for the fuel system. If this is the case---the fuel return is going to the stock 3/16" line---before you do ANYTHING ELSE move the line to the other side of the engine compartment, and connect your return to the 1/4" vapor recovery line. At the back of the car, connect this line to a vent in the top of the fuel tank. Then see what you get. This is a COMMON mistake when guys do the conversion. They think it is fine to use that dinky line, when in reality you need a minimum of 1/4". Yes, 1/16" makes that much of a difference! At idle it will run rich and stumble, but will run FINE on the road and under boost. But go back to idle or low speed low load operation and the thing just keeps loading up.

 

If you got a fuel pressure gauge, check that first. But I can tell you for positive, if the return line is using the dinky stock return line in the 240, it's going to do exactly what yours is doing, and you need to use the line I said, or run another properly sized return line.

 

For a quick check, a piece of FI hose from the bottom port on the regulator straight to the vapor line (without the check valve assembly, please!) on the left fenderwell will allow proper fpr operation with no restrictions whatsoever.

 

Good Luck, post back with what you find!

[ryan95i4]

 

For a quick check, a piece of FI hose from the bottom port on the regulator straight to the vapor line (without the check valve assembly, please!) on the left fenderwell will allow proper fpr operation with no restrictions whatsoever.

 

Good Luck, post back with what you find!

 

 

I know this is an old post, but I have similar issues.

 

I previously though the FPR was bad, as my idle pressure was over 60psi, and there was no change in fuel pressure when I pulled the vacuum line off the FPR.

 

After reading through the forums for a few hours, i see that this is likely a symptom of using the factory return line (I have a 73 w/ a L28ET swap).

 

I tried the quick check above, just switching the line from the bottom port of the FPR from the stock return line over to the vapor line, but could not get the car to even start like this. I then tried just running that line into a fuel can and again, car wouldnt start. I then moved the line back to the stock return line and was able to get the car to start again, but obviously with the elevated fuel pressure at the rail again.

 

fuel pressure at the rail when the car isnt running is 32psi and was constant when trying to crank the car in each situation above.

 

Did i miss something for this quick check that would prevent the car from starting at all?

 

Thanks,

[ryan95i4]

Just an update to this, yesterday I let the car warm up and then switch the line from the return line to a gas can and the car started up and ran great. Fuel pressure was around 28psi at idle, and jumped to 38 psi when pulling the vacuum line from the FPR. Car revved freely and when letting it fall back to idle, it feel back to idle dead on, no stumbling as it tried to find idle, and couldnt get the car to die if i tried

 

So, add me to the list of people plagued by issues caused by the stock return line on the 240's. Will run a new return line asap.

[xShodaimex]

Just wondering if the 240 return line was the same as the 260 return line.. I have this problem