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I have a LT1 out of a 1995 Impala. It starts strong but dies after about 2 seconds unless I spray short blasts of starter fluid in (tested for about 30 seconds).
Fuel psi at rail 42. But quickly drops to zero immediately when off. I will check all connections and regulator tonight, but was wondering if this would cause it not to run?
My other thought about what could be the problem would be the security system. I was told by the previous owner that vats was programmed out. (What method he used I am unsure of.) I was messing around with replacing a heater core and worry that I might have lifted a ground or pulled a wire. I am still learning but have read about a 30hz signal needed or a jumper on the starter enable relay. Is this a possibility also for my no run situation?
I have a LT1 out of a 1995 Impala. It starts strong but dies after about 2 seconds unless I spray short blasts of starter fluid in (tested for about 30 seconds).
Fuel psi at rail 42. But quickly drops to zero immediately when off. I will check all connections and regulator tonight, but was wondering if this would cause it not to run?
My other thought about what could be the problem would be the security system. I was told by the previous owner that vats was programmed out. (What method he used I am unsure of.) I was messing around with replacing a heater core and worry that I might have lifted a ground or pulled a wire. I am still learning but have read about a 30hz signal needed or a jumper on the starter enable relay. Is this a possibility also for my no run situation?
You would get no crank and no FP prime if the theft relay was bad.
Pull the vacuum line from the regulator and check if there is fuel in there. Should be nice and dry unless the diaphragm in the reg popped.
Thanks for the info about the theft relay, I will get that idea out of my head and focus on the fuel pressure. One problem at a time. I did pull the vacuum line and while there was no moisture it did small strongly of fuel. I also pulled the fuel rail and injectors and key on and pump running saw no leaking injectors. (Pulled them and placed paper towels under and had pump on for about 10 mins) The car sat for about three weeks while I had the dash apart fixing the heater core and waiting to change out the opti, so maybe it dried up? I was thinking the of renting a vacuum tester and pulling 20hg and seeing if it holds. Anything else I should check?
May help or not.But When we put a cage in my buddies car we left a tehft modual unhooked. Car would start and run good for 2 seconds and die. Checked fuel pressure and it would loose fuel pressure after 2 or 3 seconds. Hooked up the modual and it was fine. It is a 94Z
Well thanks again for the help, I borrowed a fuel pressure tester again, 43 psi with key on, then, while running on starter fluid, it dropped to about 36-38 psi. I did this for about 20 seconds. I put a vacuum tester on the FPR, and while I am not sure how if this is a good way to test, I pumped it up to 15hg, and watched it quickly drop. Tightened all the connections I could reach, new FPR will be put in tomorrow. But are my symptoms typical of a failed FPR? I am still confused on why it wouldn't run on 38psi at the test port. Could it be bad fuel? I didn't drive it at all this winter, blew the transmission.
My car has bad gas in it and will start and idle (poorly), but dies as soon as I give it gas. The gas is literally between 2 and 3 years old though!!! Its light brown and smells weird, lmao.
If it was only 2-3 months, the gas should still be good enough to drive with. Honestly if you get 38psi at idle and it jumps to ~43 when you pull the vacuum line from it I don't think its the reg, sounds more like the FP.
Puck, it was only down about 5 months and I wasn't able to pull the vac line (spray can and watching psi gauge) but will try tomorrow. Already ordered the reg, but pump is now on the list of checks for tomorrow, thanks!
I did test the injectors, average 12.7 ohms all around, and plugged a noid light into each while cranking (NOT running) and all flashed.
Waltsfastz, I read in another forum the same thing you talked about, and still trying to figure out a couple of checks for that. Need to find someone on Long Island that can verify vats is removed from PCM. Obd1 with obd2 connector and I lack the cable.
So what I need to research is, does the vats/theft module allow injectors to fire initially then shut them down when a certain signal or logic is not met. I have air, spark, (as it runs on a spray can) I have fuel psi (38-42 psi at the rail). I only tested w/ noid light while cranking, tomorrow I will do my can of starter fluid and put a noid light in one injector. To test while "running" .Just let me know if I am totally lost, or off track. Appreciate the help.
Grounding out the yellow wire on the TDR under the glove box instantly solved my problem, but it sounds like yours is something different since you can get crank and fuel priming. This is what it sounds like in your case:
If a trouble code is present (ex. DTC 46 or P1626), the computer is not receiving the fuel enable signal from the TDM[BCM]. This could be a wiring/connection issue or module failure (not a common problem as stated above). Your engine would crank, but not stay running as fuel to the injectors will be cut off. Aside from using a schematic to narrow down the problem, a bypass is also available (see below).
The TDM[BCM] modules are located under the RH side of the dashboard. If you need to replace one, a brand new module will program itself to your existing key on the first key ON sequence. A used module has a 1 in 15 chance of matching your key and cannot be reprogrammed (a BCM will also need to match the power options you currently have). You will likely have to get a new key to match the module. If you are lucky and have the key that goes with the used module, then you can have a new key made that uses it's pellet resistance and matched to the physical profile of your existing key. Without knowing the pellet value of a used module, you can try all the resistor combinations until it works or have a locksmith or dealer use an interrogator to find the value.
shbox has saved my *** more times then I can count in the ~10 years of messing with LT1s.
Ended up searching through the wiring and found a VATS bypass module tucked behind a heat vent. I guess it wasn't programmed out like I was told when I purchased it. (Anyone on Long Island that wants to do this for cash or case for of beer?) Took out the fluke and tested the black wire, no ground. Cut the wire, spliced in a new lead and ran it to ground, noid light flashed and it started right up! I still have a problem with FPR, but will fix that tomorrow.
I did change the opti which was not the issue but not sure how much longer this one would have lasted (only about 40k on engine with orginal opti). This is what happens when you melt the check valve to the Opti. These are after I wiped the disk, metal plate and some of the sludge out. Thanks again for the help and the info on this forum!
Last edited by ThomTT; 05-08-2015 at 08:19 PM.
Reason: Spelling
The cable you need is $60, and if you plan to keep the car is well worth the money. You can easily tune out VATS yourself if you had it. You can make one homemade from ebay parts for super cheap,like $20, using this post here (post #8, NOT the first post)...honestly you can easily brick a PCM by losing connection while flashing so I would recommend the "real" cable for the extra $40 though.
Again thanks, tempted to make my own, since I already have a few arduino cables around, an I am an active duty electronic technician. but will probably just buy it. I was about the order a moats cable but this one is less $$. Now I need to reasearch programming . After reading your post last night about TDM/VATS. Was thinking about installing an arduino as a bypass/security / remote start module that I can activate with a keypad to or Bluetooth. But KISS rules apply and will just deal with a hidden switch and a key.
While I am here, can you recommend software? Also can't I just take a junk yard obd1 connector and cut out my obd2 and swap them out. Obd1 is just two wires and a ground I thought.
While I am here, can you recommend software? Also can't I just take a junk yard obd1 connector and cut out my obd2 and swap them out. Obd1 is just two wires and a ground I thought.
I use an older version of TunerPro RT. I think my .xdf data definition file (what lets the software know what all the data for your particular computer means) was a free download from moates. I think there is a free version with "nag screen", so no features are missing and you can use it as long as you want but every time you turn it on there is a 10 second window that you can't skip. Basically you can get up and running with OBDI with just the cost of a cable and cheap laptop or netbook.
You are correct that normal OBD1 is only 3 cables, on an OBDI car ground goes to A and the other two go to M for Data. I know they make cheap chinese adapters for the cables so I'd imagine it wouldn't be impossible to convert the connector...shbox has the goodies once again
05-07-2015, 09:52 AM
LT1 only runs on starter fluid, 
