LT1 Starting Problems

[auroradan]

I have installed a 94 LT1 (bone stock) from an ex cop car into my 86 S-truck. Yesterday I was able to start her for first time, had a bit of shaking [probably air in fuel rails] but she did light up. Now the problem, she shuts down after about 2-3 seconds of running. I can try again and she will repeat same problem.



Now I do not have everything hooked up, mainly the cooling system, I want to leave it out until I get this bug taken care of. I only plan to see that all is operating as it should before taking up all the available work space with radiator and dual fan setup.



I had Current Performance build me a custom harness that matched my engine electrics to the truck electrical system (his harness actually plugged into my stock firewall plug!) All engine emissions are retained as well as the dual cats and a quiet exhaust.



Fuel pump, filter and hoses were replaced with a new one that would go to a 94 LT1. To me the engine sounds like the computer is shutting it down.



Here is a short video (http://tinyurl.com/3x96cd) of my engine starting and stopping.



I also have an identical 94 Cop Car (daily driver) and I use it to help me setup the truck. I bought the donor cop car and pulled all the running gear before scrapping, it did run perfectly the day I pulled the engine/trans.



Sure could use your help guys,

Dan

[spacecadet]

Check the oil pressure switch. If the computer doesn't see oil pressure it will shut off the spark.



Space.

[spacecadet]

I seen your pics. I'm impressed with the exhaust that you made. I'd suggest posting on your pics here as I'm sure they would help some 'newbie's and old guys with new ideas.

Space.

[auroradan]

Mr. Cadet,



Not sure about the Oil pressure sensor. The one that came with my harness has only one wire. I assume it goes only to the dash gauge, and that seems to be working fine. I'll look through my Helm books and see if I can figure it out.



Thanks for the Kudo's on my scrap yard exhaust pipes. I set out to just make a temp hookup to the stock 2.8 muffler until I could afford a real exhaust job. Since my old pipes are in such good shape (almost no rust) I decided to just do it right and have it until it rusts away. I ended up tee'ing the two cat back pipes into the one 2.8 muffler. I know I'm loosing some power, but I'm over 40, so I'm in no hurry to calibrate any troopers laser gun !! It does have a subtle tone (what few seconds I get!). It also allows me to get away with leaving some rubber behind without drawing too much attention to myself ( I dream of leaving a huge smoke cloud next to some high school ricer and let the boys in blue go after rice boy !).



Dan http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif

[spacecadet]

"Space", "airhead" or "late to diner" is just fine by me. Please, not "Mr", don't make me out to be as old as I already am. http://www.s10v8.com/images/smilies/icon_wink.gif http://www.s10v8.com/images/smilies/icon_eek.gif http://www.s10v8.com/images/smilies/icon_wink.gif Blazer, race car, trans am, my wife says it just a mid-life crisis that started in my mid-teens. http://www.s10v8.com/images/smilies/icon_smile.gif I just call it normal ...life.

I will do some checking tomorow for that system on your truck.

Once you get that system set up perfectly you WILL like it. MY buddy just put one in his 4x4, Man that thing is pretty wild! And a lot better on fuel than my carbed blazer.

Space

[ymyhere]

auroradan

A couple of thoughts on your issue. Have you put a fuel pressure guage on and watched it as you start the engine? Your fuel pump will run for a few seconds when you key on to prime the rails, then shut off. The ECM may not be kicking it back on. Watch the guage as it starts and see if it holds pressure. Another thing is your IAC (Idle Air Control) working? If the engine has set awhile before you installed it, it may be stuck in the closed position and not working. You may have checked all of this already. You will LOVE your LT1 in your S10

Gary

[auroradan]

Space,



I spent some time last night and posted about half dozen pics of my LT1 build Just waiting for Mike the Grand Pubah to give his thumbs up (or off with my head!).



Looked through my factory manuals, but they are tricky to read. I'll have to spend more time looking through them, unless someone else has the same books and can better tell me what page to look up.



AuroraDan http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_cool.gif

[auroradan]

Gary,



The engine did sit on the engine stand for about a year, so I will look into the IAC and see if it is stuck.



Do not have a gage to check the fuel pressure [yet], but I did install a new fuel pump and lines that are correct for the motor. I do hear the pump prime for about 3-5 seconds and it is also running for a few seconds after the engine dies. When the engine dies, it does so promptly like the ignition shuts down, not a sputter like might happen when the fuel pressure is weak.



I drive a 94 Caprice ex cop car for my daily driver with the identical LT1, I do love that powerplant! It's almost tricky to drive on wet streets, she will break the tires loose with any heavy touch of the throttle http://www.s10v8.com/images/smilies/icon_biggrin.gif I suspect my pickemup may be a real pain on slick roads, may have to load the bed with a dozen dead 2.8 motors http://www.s10v8.com/images/smilies/icon_eek.gif for traction.



Thanks for your tips and keep them coming!



AuroraDan

[spacecadet]

I wasn't able to get that info on lunch today. But I will try tommorow.

Space.

[auroradan]

Another thing is your IAC (Idle Air Control) working? If the engine has set awhile before you installed it, it may be stuck in the closed position and not working. You may have checked all of this already. You will LOVE your LT1 in your S10

Gary



Made it home from work early, so I was able to check the IAC. Removed it and checked with ohm meter, all is fine, even voltage input. It did have a bit of carbon, did not look excessive, I polished it on the wire wheel and re-installed. Started again, no difference still quits after a few seconds.



Just for kicks, I swapped the MAP sensor from my 94 cop car, same results.



Back to the thinking chair http://www.s10v8.com/images/smilies/icon_smile.gif



Aurora Dan

[ymyhere]

Swaping out your MAP sensor sounds like your game for the old trial and error method. How about swaping computers? Where do you have yours mounted on your S10? If they both are easy to get to, give it a whirl.

[auroradan]

I sorta swapped out the computer before. About six months ago I bought my second cop car, a 94 LT1 Caprice for $1k with 84k miles from the state. It came with a transmission problem, would not at all shift into 3rd or 4th so I did a computer swap (truck was still in a million pieces) to see if I would get lucky and just have a bad PCM. No luck, the Caprice still would not shift but otherwise operated normally, so I sprung for a new (rebuilt) trans.



I'm now 99.9% sure my problem is wiring harness, the engine shuts down smartly like the PCM is behind it. The motor just runs so smooth (albeit 4 seconds worthhttp://www.s10v8.com/images/smilies/icon_wink.gif that leads me to the wires.



Until I chat more with my harness builder, I think I'll continue mounting the little things, like Radiator and dual fans and entire front of the truck. Also put the dash back together (took me an entire afternoon to locate the damn 2.8 computer!).



Question: is there anyone in the Portland OR area that has a better understanding of my LT1 electrical system? Maybe if I could get someone here in person that may spot my problem ??



Keep your ideas coming!



AuroraDan

http://www.s10v8.com/images/smilies/icon_cool.gif

[offroader16]

I just did this swap in my 99 s10 i also got a lt1 from a 94 caprice cop car and if you can find the diagrams for the security system you will find that even though there is no chip in the key that there is a module that will shut down the fuel pump or spark i can't remember off the top of my head but i had the same problem. the module was located under the dash of the car and needed to be wired in to operate correctly. Hope this helps let me know if you need more info i will see what i can find on it.

[auroradan]

if you can find the diagrams for the security system you will find that even though there is no chip in the key that there is a module that will shut down the fuel pump or spark



Offroader,



That's a new to me. I thought that sine my key does not have a resistor in it that I had no security to worry about.



I have a connector in my harness that I cannot find what t goes to. <hr width='200'><img src='images/jpg.gif'>: <a href="http://s156.photobucket.com/albums/t4/auroradan/S15%20V8/?action=view&amp;current=PICT2061.jpg" BORDER="0" target=_blank><font size="-2">image will open in new window</font></a><hr width='200'>


Could this be what you are talking about?



I do have manuals, Haynes and the three book set from Helm. Looks like I have a new reading assignment! http://www.s10v8.com/images/smilies/icon_biggrin.gif



Thanks for the new lead,

Aurora Dan http://www.s10v8.com/images/smilies/icon_biggrin.gif

[auroradan]

Okay,



We may have an answer! According to my GM Service Manual the "PASS-Key 2" Theft Deterrent System is standard equipment on 94 Caprice, Roadmaster ect. Now my 9C1 ex-police car does not use the PASS key system, I just ran outside and checked with my spare key ($1.99 plain hardware store key) it started my cop car just fine. Also there is no "Security" light on my dash. In the past I had an 89 Camaro with the security key, had "Skippy" http://www.s10v8.com/images/smilies/icon_confused.gif cut me a new $35 key only to have it not work! Turns out he miss read the key interrogator and gave me the wrong coded key.



So my thought here, http://www.s10v8.com/images/smilies/icon_confused.gif is that the mystery connector is for the PASS key thingy http://www.s10v8.com/images/smilies/icon_biggrin.gif



AuroraDan http://www.s10v8.com/images/smilies/icon_cool.gif

[auroradan]

you will find that even though there is no chip in the key that there is a module that will shut down the fuel pump or spark

I have a response about my mystery connector, it goes under the dash near where the factory had the 2.8 computer located. It operates the dash check engine light, OBD signal, Park/Neutral switch, ground wire and one Tan wire unknown what it does. Since I plugged the original hole in the firewall for the old computer wires (too close to left exhaust manifold anyway), I'll have to find a new route for this small bunch of wires. I mounted my LT1 computer on a second gen S10 coolant recovery tank, next to the battery on fender well.



Posted the same question to a couple of other groups (sorry, my bad :icon_razz: ) and the consensus is that I do have the security kicking in and shutting everything down. Others have said I need to have my computer "Flashed" to remove the security problem. My question, does anyone know of a Portland Oregon area fellow/shop that can reprogram my PCM, or do I need to ship it off to a re-education camp :icon_razz: ? If I do need to ship off, what are your recommendations?



A-Dan :icon_biggrin:

[ymyhere]

Any updates since your last post?

[auroradan]

Ymyhere,



No major advances in the last week, spent most of the time trying to find a local fellow who can reprogram my PCM. No luck so far, so it looks like I need to wrap up the computer and ship off for re-education!



I did tinker with the Air pump and made a trip to the You Pull It wrecking yard for stock GM relays and bits of hose (trying to find a better brake boost hose to fit under my Corvette injecdtor covers).



A-Dan http://www.s10v8.com/images/smilies/icon_cool.gif

[jmayhew]

I am still trying to figure my truck out,I just watched your video of your truck start-stop,my truck seems to be doing exactly the same thing with a vats bypass module installed,I also called Jared at Current Performance and he said to use OBDI port to scan it,I tried but unable to read any codes,we both have LT-1s,current performance wiring,and have not had the pcm reprogrammed,do you think thats the problem with both trucks? http://www.s10v8.com/images/smilies/icon_eek.gif

[stonebreaker]

It's not a security problem. The passkey system doesn't act like that - it will simply not allow the car to start, period.



I agree with space cadet, check your oil pressure switch. The computer is programmed to shut the motor off if it doesn't see oil pressure within a few seconds of startup.



Check with these guys: <a href="http://www.impalassforum.com" target="_blank" target="_new">http://www.impalassforum.com</a>

[red1997blazer]

What does it do when you start it and immediatly floor it? From your video it never has a chance to enter closed loop.



A neat tool if you have a lap top is tuner pro. It's free, you just need to buy a cable from www.akmcables.com.



One thing you might try is to wire the fuel pump on start it and if the truck runs it's almost a sure thing the oil pressure switch is the culprit. You can also unplug your maf to eliminate that sensor while your diagnosing the problem. With the maf unplugged it will just use the map sensor. That way you can eliminate faulty wiring since you tried swapping the maf's already.

[auroradan]

StoneBreaker &amp; Spacecadet and jmayhew,



http://www.s10v8.com/images/smilies/music342.gif



After reading Stonebreakers posting I did some reading in my GM manuals for 94 Caprice &amp; Buick. Looked at the Oil Pressure switch and traced out the wires.



Looking at the sending unit connector, Current Performance (CP) has only one TAN wire, position "A". That goes to Instrument panel. CP has no other wires to my Oil pressure sender.



According to my GM electrical diagram, three wires are used.



"A" TAN wire, instrument panel (Dash Gauge) This wire is in connector from CP. Pic of CP Oil Connector (http://s156.photobucket.com/albums/t4/auroradan/S15%20V8/?action=view&amp;current=CPHarnessOil.jpg)



"C" ORANGE wire, goes to PCM Black connector B31. It is positive 12 volt (not used on CP harness)



"D" GRAY wire, goes to Fuel Pump relay. Also not used on CP harness, but my fuel pump is running after my engine shuts down. Pic of Factory Chevy LT1 Oil Pressure connector (http://s156.photobucket.com/albums/t4/auroradan/S15%20V8/?action=view&amp;current=Factoryoilconn.jpg)



So, based on what my [victim of public edumacation] brainhttp://www.s10v8.com/images/smilies/icon_crazy.gif concludes is that the PCM (computer) does NOT get any signal from the oil pressure switch.



I'm expecting my VATS module from CP anyday, I'll update http://www.s10v8.com/images/smilies/user.gifafter that is installed.



I'm also still open to suggestions from anyone here who has other ideas. You can also PM me directly if you like.



Thanks,

A Danhttp://www.s10v8.com/images/smilies/shake.gif

[auroradan]

red1997blazer,



What does it do when you start it and immediatly floor it? From your video it never has a chance to enter closed loop



I have played with the Throttle in the precious few seconds of running I get, engine does rev up according to my foothttp://www.s10v8.com/images/smilies/burnout.gif. No problem in that department. So looks like no fuel problem to me, pump is running few seconds after shut down.



About the open/closed loop, I misspokehttp://www.s10v8.com/images/smilies/icon_redface.gif. You are correct, never enters closed loop. I'm still learning about this fancy schmancy fuel injection stuff!



A-Danhttp://www.s10v8.com/images/smilies/goofysmiley.gif

[jmayhew]

I shipped my pcm to Bryan at pcms for less today to tune it for my truck without vats,I also do not understand the current performance wiring harness,if this pcm tune helps my truck I will let you know asap

Looks like Jared at CP is about as helpful to you as he is to me,he emailed me a wiring diagram that not even close to the harness I paid him over 900 to build,wish I would have built my own harness and used most of the money for Cold Beverages :icon_razz:

[auroradan]

Latest update:



Today the mailman brought me a VATS delete module from Current Performance. After installing I eagerly turned the key hoping for my engine to come to life. But today is not my day http://www.s10v8.com/images/smilies/icon_frown.gif Engine started great as usual then died as usual http://www.s10v8.com/images/smilies/icon_cry.gifhttp://www.s10v8.com/images/smilies/icon_cry.gifhttp://www.s10v8.com/images/smilies/icon_cry.gif



Double checked my wiring (there are only three) and all is 100%.



Jmayhew is having identical problems with same engine. He has his PCM out for programing, guess I'll wait to see his results. Right now the truck is 99.9% done and collecting dust. http://www.s10v8.com/images/smilies/icon_cry.gifhttp://www.s10v8.com/images/smilies/icon_cry.gif



A-Danhttp://www.s10v8.com/images/smilies/icon_cry.gifhttp://www.s10v8.com/images/smilies/icon_cry.gif

[auroradan]

SUCCESS!!!!



Today my neighborhood postman brought me a reprogrammed PCM (computer). Home late from work, its dark and raining.... so what am I doing??? installing my PCM of course.



With my heart pounding, I turned the key. rumble rumble my engine comes to life AND STAYS THAT WAY!!! http://www.s10v8.com/images/smilies/icon_headbang.gifhttp://www.s10v8.com/images/smilies/icon_headbang.gifhttp://www.s10v8.com/images/smilies/icon_headbang.gif Topped off the power steering (to remove that Ford sounding PS pump growl http://www.s10v8.com/images/smilies/icon_biggrin.gif )



No wipers, no brake lights and the headlights one pointing in the ditch and the other at the Moon, so I put her in gear. So far so good, slow trip around the block couple of times looking for problems or loose parts. Quick stop in the driveway (it's now down pouring buckets) and all checks out, only a bit of oil smoke coming off the exhaust manifolds. Time to "exercise" the pistons. Head out for the road. Slowly drive to 55 ish, then stop and look around, engine still puring and no parts dragging behind. Hop back in, and well, lets just say the speedo needle climbed to places the lowly 2.8 could only dream of http://www.s10v8.com/images/smilies/fun_11.gif http://www.s10v8.com/images/smilies/fun_11.gif http://www.s10v8.com/images/smilies/fun_11.gif.



It's getting late, wife is asking (again) when dinner will be ready , so I put my new toy to bed. I have to work all weekend, so I wonk get too much "Playing" http://www.s10v8.com/images/smilies/burnout.gif



Next week I'll try to get some fresh videos uploaded.



LT1's RULE!! http://www.s10v8.com/images/smilies/beer.gif http://www.s10v8.com/images/smilies/icon_drink.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif



A-Dan http://www.s10v8.com/images/smilies/icon_smile.gif

[Melonhead]

Congrats on the adventure. Time to make the truck legal and do more illegal activity, like burnouts. http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif

[jmayhew]

YAH-HOOOOO,I am very glad to see that also have your truck running,because of the weather pattern lately in my area I have not even got my truck out of the garage yet for any kind of test,but I know firing er up and having it run until you tell it to shut off is a good thing http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif http://www.s10v8.com/images/smilies/icon_biggrin.gif

[aceez71]

I'm more of a TPI guy but the systems are very similar. I second the fuel pressure. Sounds like the fuel pump relay is dropping out. Was the video in real time or did you let the fuel pump prime prior to each start. As smooth as its running it sounds like the fuel is being cut off. I did have one other similar issue on an IROC once that turned out to be a clogged muffler. wow i just realized this is 4 month old post. Hope you fixed it!!

[aceez71]

somehow all the posts weren't showing uppast the february posts lol! GOOD JOB!

[grinch]

doe yoe check to see if the VATS module was bypassed?