L28ET problems. Runs great, and then nothing

CamH · Post by **CamH** » Sun Apr 19, 2009 2:47 pm

Here's what I've got:

1983 rebuilt L28ET with forged bottom end with compression bumped to 8:1
Factory distributor
Good condition factory turbo injectors
No intercooler
Factory turbo in good condition
MegaSquirt II v3.57PCB
LC-1 wideband O2 sensor
MSA downpipe
240Z coil
NGK BPR6ES plugs gapped to .020

Here's what it's doing:

When I start the engine, it starts up almost immediately, and runs very well. It revs easily and is very smooth, and idles nicely. After short time, it will begin running very poorly - extremely rich according to my wideband. After that, I can rev it up and once I let off the gas the engine will immediately die, and I cannot restart the engine until I turn the MS off and then back on.

I really need to get this sorted out because I am about ready to give up on this engine and put in a different one with carburetors soon because I really need to be able to drive this car. Thanks in advance for any help.

Matt Cramer · Post by **Matt Cramer** » Mon Apr 20, 2009 6:39 am

Do you have a data log of this problem happening? Please post it along with your MSQ. This will give me a better picture of what's going on. Once I have these I can look over it and see what I can do to help...

niner11 · Post by **niner11** » Mon Apr 20, 2009 7:39 am

Matt is right you need to post a datalog for anyone to know where to start. With a 3.57 board its unlikely that you have problems related to assembly. When I first got my MSII setup working in the car it would idle wonderfully and even drive for very shot periods of time but after driving it would begin to miss and eventually die completely. Turned out to be incorrect dwell setting in MS. Changed to an aftermarket 12.00 generic coil with the correct dwell settings. Thinking that misses might show up as rich indications on an AFR gauge.

CamH · Post by **CamH** » Mon Apr 20, 2009 2:26 pm

Unfortunately, I do not have a data log for the particular way it is running at this time. I left the power cable for my laptop at home the last time I went to work on the car. I do, however, have a copy of the MSQ file I am currently running. Could I please get someone to look it over before I rip out my nonexistant hair? I can get a datalog to accompany it probably tomorrow evening.

CamH · Post by **CamH** » Tue Apr 21, 2009 6:46 pm

Here is a datalog of exactly what the car is doing. This was with the MSQ posted above.

CamH · Post by **CamH** » Tue Apr 28, 2009 5:13 pm

Alright, guys. I fixed the issue that I was having when I started the thread. It was due to my fuel pressure being too high. Now I am working on dialing in my VE table. It seems like when I can lower the VEs to the point where the car is a lot more lean (no more watering eyes!) but the wideband seems to shoot all over the place. Could there be something wrong with the wideband from running too rich for too long? Is it symptomatic of a bad wideband to report numbers that are all over the place?

Another issue I am having is that when trying to restart the car once it has warmed up is extremely difficult. I changed my Warmup Wizard setting for Pulsewidth at 160F to 25 (which is higher than the cold start setting of 15) and it made it so the car will start after cranking on it for a while, but it doesn't seem correct. Can I get some help with this?

grippo · Post by **grippo** » Wed Apr 29, 2009 6:10 am

Definitely put the PW back to what it was unless you haven't tuned your cranking pw when cold. There are 2 things to try. When you do the hot restart, do you cycle power (turn the key all way off) ? If not, try this. If it fixes the problem (uses the hot running pulse tolerance unless you cycle power) then switch to code 2.890 and you won't have to cycle power any more. The second thing is to check the hot restart option. This option allows you to use or not use ASE on hot restarts. Try changing this.

CamH · Post by **CamH** » Mon May 11, 2009 8:14 pm

Here is a recent datalog and MSQ file. I am still having problems with the acceleration settings. I still haven't tested the fuel pressure, but I ordered a nice pressure gauge and will be installing it as soon as it arrives so I can verify that I am running the correct fuel pressure.

CamH · Post by **CamH** » Sat May 23, 2009 4:42 pm

Alright, guys, I just got back from messing around with the car. Someone on another forum pointed out that my MAP reading was way off and I had the vacuum line for the MAP sensor in the wrong location (bottom of the throttle body.) I relocated the MAP sensor and put the fuel pressure gauge on it.

Nothing but trouble! According to my fuel pressure gauge, I've only got 1PSI of fuel pressure when the fuel pumps are running - even if I smash the return line. Could this be indicative of a bad fuel pump or a bad fuel pressure gauge? I'm not sure! I tried running the car like this and it would run for a few seconds and then die down and not start again for 20 or 30 minutes. Amazing!

With the MAP sensor relocated, I've got like 80-90KPA during cranking. If the car starts, it goes down to 60KPA which is probably about right! Of course, the car won't run long...

A side note: A few months back, I ran the fuel tank dry and the fuel pump was running for a few minutes dry. It got extremely hot and blew my fuse for the fuel pumps. Is there a chance that it would have been fine for a few months before blowing out all the way?

Also, I don't think it has anything to do with getting a proper reading for the MAP because I disconnected the line for the MAP sensor so it would read about 100KPA the whole time and had the exact same symptoms.

I'm not against buying a new fuel pump if it sounds correct that it is ruined but it seems odd that it would stop working the same day I fix the MAP.

What do you guys think?

Matt Cramer · Post by **Matt Cramer** » Tue May 26, 2009 6:52 am

I'd try wiring the fuel pump always on for testing, and see if you can build pressure that way.

CamH · Post by **CamH** » Tue May 26, 2009 5:58 pm

Update on the car! The walbro fuel pump was completely dead. I replaced it with a 65GPH high pressure Bosch inline pump. With the current tune, the car starts up almost immediately and revs up fairly smoothly. I was very happy with it.

I datalogged a run up and down the street, and then drove the car to have the exhaust put on it. The exhaust is going to be a 3 inch with a straight through magnaflow in the middle and a resonator on the back. It will be done tomorrow.

I'm attaching the datalog to this post for everyone's review and suggestions. It is using the MSQ file from my last post.

Also, the first thing I said when I stepped on the gas was, "Holy poop!"

MSefi.com read only forum (Jan.15,2018)

L28ET problems. Runs great, and then nothing

L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing

Re: L28ET problems. Runs great, and then nothing