All I did was disconnect the battery and took off plug wires to remove the tunkside exhaust to weld up a leaking header and weld a wideband bung in the down pipe. I also replaced the map sensor. With a new one. It cranks and I have fuel pressure. I also checked and verified spark on two random wires. I also noticed that while cranking the temp guage peggs which it never has before. Any suggestions?
------------------ 86 SE Convertible 3800sc 4t65e HD.
Fuel pressure does not say there it fuel to the cylinders, but spark does say there is spark to the cylinders, so if you have spark then you have no fuel. Larry
Fuel pressure does not say there it fuel to the cylinders, but spark does say there is spark to the cylinders, so if you have spark then you have no fuel. Larry
I wonder what happened then to cut the fuel, yeah I just went out and cranked it for several seconds and pulled the number 4 plug and it was dry.
------------------ 86 SE Convertible 3800sc 4t65e HD.
I hooked up hptuners and scanned as I cranked it over and nothing readin on the injector duty or either injb1 or injb2. Looks like up the injectors ain't firing.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Yeah but what did I do to stop them from firing is there some wires specifically to check? Also I'd the temp guage pegging have something to do with this?
------------------ 86 SE Convertible 3800sc 4t65e HD.
If you are sure you did not do anyting else then the MAP sensor is the only difference in running and not running. Put the old one back. Larry
There's a bulkhead connector that goes through my firewall into the cab where the comp is. That enables me to leave the computer there and disconnect the motor for easy drop out. All I did was unbolt it but not disconnect it to move it to the sides bit to be able to pass the wideband wires through. That's why I'm wondering what wires control the injectors. I will have to recheck but when I was checking for power as the injector wires I think there was power to both wires even while cranking.
------------------ 86 SE Convertible 3800sc 4t65e HD.
Check to make sure you have battery power to the ECM and was any welding done on the exhaust with it bolted to the engine with the battery and ECM connected as some computers will get damaged while welding especially with a mig. Dan
Check to make sure you have battery power to the ECM and was any welding done on the exhaust with it bolted to the engine with the battery and ECM connected as some computers will get damaged while welding especially with a mig. Dan
No it was done with the exhaust off the car. I'm pretty sure I have ECM power as it cranks over and I get some readings in hptuners.
------------------ 86 SE Convertible 3800sc 4t65e HD.
[This message has been edited by Tweeder (edited 10-09-2013).]
Welli found the problem, it's the new map sensor, I unplugged the new one and plugged it into the old one but left the vacuum line connected to the new one. It took a few cranks but it fired up. I left it running and plugged it back into the new sensor and it stayed the same. If I shut it off and restart it in the new, it won't start. I figured out the 4% TPS, the throttl cable was snagged. This is the sensor I bought. http://www.ebay.com/itm/231...id=p3984.m1439.l2649
Andy suggestions as to why the new one don't work?
Is your MAP sensor connected to the correct vacuum? It needs to be connected to lower intake manifold vacuum not the vacuum sources between the throttle body and the SC. The LIM vacuum port is located under the snout of the supercharger. That one should run to the fuel pressure regulator, the MAP and the BBV if you have retained it.
The vacuum sources between the SC and TB should connect to the power brake booster and to the evap solenoid, if equipped.
If connected to the correct vacuum source, what does the MAP sensor read with the key on engine off? It should read about 1 bar or 30 inHG or 14.7 PSI. That is normal air pressure at sea level.
Oh - and your temp gauge always pegged when you turned the key to start. GM fked up on the design of the wiring for the temp gauge/temp light. Leaving the temp gauge pegging will over time cause your temp gauge needle to slip on it's post and will cause it to be inaccurate.
To fix - at C500, swap the pins D3 (Dk Green) and C2 (Dk Green/Yellow). Then follow the dash swap on this page. http://www.fierosails.com/tempgage.html You have to do both swaps or the result is you will leave your temp gauge disconnected.
You have to do the engine bay fix at C500 rather than at the temp sender because your 3800 does not have a dual temp light/temp gauge sender. If you followed Ryan's sheet, you now have the PCM controlling the temp light and the gauge running to the green wire of the 3 pin dual (CTS & temp gauge) CTS sensor.
One you have preformed both swaps your temp gauge will no longer peg when the key is turned to start, and the TEMP light will come on during cranking (check bulbs) like it is supposed to.
Remember you have to pull the fork out of C500 before you attempt to remove the pins. Even after removing the fork you still need to depress the tang of the terminal to get the pin to back out of C500.
It makes me feel the world is just a bit more 'correct' when I see the TEMP light come on during cranking.
[This message has been edited by phonedawgz (edited 10-10-2013).]
Is your MAP sensor connected to the correct vacuum? It needs to be connected to lower intake manifold vacuum not the vacuum sources between the throttle body and the SC. The LIM vacuum port is located under the snout of the supercharger. That one should run to the fuel pressure regulator, the MAP and the BBV if you have retained it.
The vacuum sources between the SC and TB should connect to the power brake booster and to the evap solenoid.
I belielieve I have them correct, i've been running it for a couple months this way ( fuel pressure regulator to a T. One goes to the port under the snout in the LIM and the other to the map on the firewall). I have no bbv or evap. The purge solenoid is by itself from the fuel tank to the port on the side of the throttlebody. I have the octopus thingy blocked off except the large that goes to the break booster.
Thanks for that info on the sender, to tell you the truth, i've never noticed it during cranking, I only seen that it was operational durring running. I will do this correction this winter. ------------------ 86 SE Convertible 3800sc 4t65e HD.
[This message has been edited by Tweeder (edited 10-10-2013).]
Well if it's hooked up correctly then the thing to do is to look to see if the PCM is reading the MAP correctly. Key on engine off you should be able to see the MAP reading. Like I said at rest it should be the equivalent of 1 bar/30 inHg/14.7 psi. Then check to make sure the pressure goes down when you apply vacuum to the MAP and pressure goes up when you apply some air pressure to it. Don;t blow it up with compressed air, it can only handle 14 psi above atmosphere. If the indicated pressure moves in the opposite direction of the actual pressure that would indicate you have the Black and Gray wires swapped.
A - Black - or Orange/Black - Ground B - Green - Signal from MAP -> PCM C - Gray - +5v reference from PCM.
My guess is the MAP is not reading correctly for whatever reason. If however it seems to be reading correctly, and electrically connecting the MAP makes the engine die, that would seem to indicate a problem with the programming of the PCM.
If wired correctly, but the MAP reading still seems messed up, what did the old MAP sensor scan as in the same situations?
