L28ET rebuild engine that runs rich after warm-up!

[jkh280zx]

Hi All,

My first post was on the thread ‘first experiences with a Zcar’posted by cygnusx1, recently. My second post involves the same car, a 1983 280zxt, which is in the shop for a “do-over†of its L28ET. Well, this engine is now a L30ET (w/ upgrades), which currently is back into the engine bay. [The upgrades are noted below.] First attempt to start went fine. The next day, the car started fine but after a warm-up period, the car ran rich and then died. To start the car a second time, one has to push the gas petal to the floor then it starts, eventually. After setting for a few days, these same symptoms appeared after re-starting the car when it has warmed up. When the mechanic takes out a spark plug immediately after the car dies, then he finds fuel on the plug. The mechanic has lowered the new adjustable fuel-pressure regulator (AEM) to 30 psi and it runs fine but then the same symptom re-appears. [regulator set as noted in schematic by BRAAP & other posts in HybridZ] The car starts best at 35 psi so far. The mechanic looks at ALLdata (a computer program) that discusses ways to test sensors and the like but has not come up with a better way to find the problem. He suspects the MAF meter. He plans to switch out this original MAF for another from a friend's car to see if this identifies the problem. Isn’t there a little switch (or sensor-connector) that can go bad/get dirty over-time in the MAF; maybe this is the problem. But just all at once. My Zcar started for me almost all of the time during the first 300K+ miles, before the engine problems started. The original ECU is still in control of this car and reads from the MAF. I would appreciate your input. I thank HybridZ and all who put so many threads at this site. I will post this “do-over†journey with pictures when finished. Credits will be noted.

John (jkh280zx)

 

Components Kept: a complete performance cam kit that originally was added at ~170K+ miles and a near new OEM turbo set of fuel injectors (256cc) that was added at 287K+ miles. Upgrades include the following: re-built kit consisting of pistons, etc. for the F54/P90a, a 60TB kit w/ plastic spacer (PAllnet), a complete turbo barb fuel rail system with its fuel gauge (60 psi) (PAllnet), 105 amp alternator (Zselect.com), cold air induction system (MSA), oil cooler kit (MSA), new turbo oil pump (ebay), a turbo high-pressure EFI fuel pump *NR* (95 psi)(ebay), NGK BPR6ES-11 spark plugs (ebay), turbo electronic distributor for 280zxt (ebay) and new distributor cap & wires (local), new water pump (local), new timing-chain kit for 280zxt (ebay), an adjustable fuel-pressure regulator (1:1 ratio of vacuum to boost) (AEM), new Garrett T3/TO4E trim w/ .63 a/r housing, a down pipe constructed w/ ports for the wastegate and oxygen sensor, and an air intercooler system has been purchased (sourced via HybridZ).

[pallnet]

When you say "MAF" do you mean AFM?

MAF= Straight through tube with a sensor hanging in the middle.

AFM= A "box" with a flap that has a sensor attached to the flap.

 

With the idea that you have all the stock 82-83 turbo EFI parts, I would think you to break out the DVOM and FSM to check the coolant temp sensor, AFM, computer or a possible short in the harness. They are in the order I would check them. You really need a FSM or at least some copied pages from one if you don't have one on hand.

[jkh280zx]

Thanks Peter,

I will relate this procedure tomorrow. My copy of a FSM is not very clear; need to get one from ebay or Nissan. I am sure that the shop has a DVOM. Your message lead me to other information:resources that needs to be checked out as well. Will let you know the results of this find. Thanks again. I am pleased with your products in my Zcar. She will be fine!!

John (jkh280zx)