There should be lots of gas flowing in the return line by using a 140gph pump and there should be lots of fuel out of the injectors if your put power to them while the pump is running. You have some kind of fuel supply problem. Are you sure the pump didn't fail?
Excellent news.! The 72 c10 lives again gentlmen. My buddy came over and we threw down on the truck and disassembled the throttlebody and discovered a plug in one of the gas ports. Cleaned that shit out, noid tested the injectors just for certainty and slammed it back together and started it up. Thanks to the forum for all of the suggestions and ideas.. Got me some TBI in my 72'
So back at work on my truck. I am having trouble with the idle when I hook up the map sensor, it makes my engine idle up and down like its gonna die and then bursts back and stays running. I am pretty sure my map sensor is ok because I tested it with vacuum using a separate power supply on a bench. If I disconnect map it idles fine.-Wierd! I think it might be my ground wire on map. I am curious if it is ok to directly ground the map to the chasis and not through the ecm at pin D2 as it says in the schematic. Does this make a difference? I am just curious. The tbi conversion outline on page: http://www.gearhead-efi.com/gm-ecm-p...on-wiring.html says to ground this pin to the chasis which is in contrast to the schematic that grounds through the ecm.?
Last edited by Tyree; 06-25-2014 at 07:19 AM.
Do not tie the sensor ground wires to the engine block or to chassis ground anywhere.
yeah I didn't think so, I was just didnt know for sure on that one. So I am still stuck with this rough idle situation only when I hook up my map sensor. It was running shitty, I disconnected the plug and it went back to running fine. Anybody have any ideas on that? I have another map sensor coming in the mail, but as far as it looks when I test this map sensor it seems fine.
Frequently a hunting idle is a vacuum leak. Get a propane torch and use it (unlit of course) to check for vacuum leaks.
Square body stepsides forever!!!
It's likely going lean. It must default back to a %TPS operating mode when the MAP is missing and that likely adds more fuel.
Did you get it warmed up so it went into closed loop? If yes, what did the BLM do?
What bin are you using? I was playing around with different bins just for s&g and had a couple of 7.4 bins that would do that when they went closed loop. Never tried unplugging the MAP, just went back to the original bin.
68 Cadillac, 472 & TH400 w/7.4L TBI and EBL **sold**
93 K1500 short step, 5.7 & NV4500 and EBL
68 C10 LQ4/TKO swapped
I am using a stock 1227747 and I just connected a new map, same problem only when I hook power plug to the map does it start to run shitty.. Runns perfectly until I plug in the map. I let it idle approx 20minutes. I am at a loss and need to take breather off this or I am gonna get sick from trippin on this truck.. I dont see or hear any vaccum leaks, but my next step is that I am going to hook up a vacuum gauge to be sure. Thats all I can do at this point. Anybody have any other suggestions?
Thanks
Well with no MAP reading it should be close to 100KPA and adding fuel like crazy. MAP plugged in should read close to 30-35 KPA on a stock motor at sea level so that would be taking away fuel.
What's your fuel pressure? What size injectors do you have? What engine? What chip BCC code?
Also once a MAP error is set it may be running the engine in LHM... so clear codes, hook up MAP and start it.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
This is in a 94 chevy 350 engine. the BCC code is ANLW, stock injectors, stock fuel pressure on new pump. Everything stock, just trying to get it running right. Engine idles and starts up great until I plug the map in then it goes stupid. I did clear the codes and start it with map hooked up and it barely started and then died. Took the map connector out of its socket and it idled great again.. triple checked my wiring and grounds. Im lost now.
letters on the ECM white label: 86ANLW K383440101 Is there a way to know what vechicle this came out of?
This is a 1227747 ECM
Last edited by Tyree; 07-02-2014 at 08:48 AM.
ran a vacuum check and I am getting 20 in Mg without map, and approx 22 in Mg with map. I got it to run good by some miracle after I did a vac test just to try again and it ran good. I tried to replicate this again an hour later and it started running like shit and died again with the map plugged in. -Lost on this one
Maybe you have a vacuum leak or bad connection in the plug to MAP? Something happened when you were messing with it.Have you checked fuel pressure yet? MAP hooked up or unhooked changes what the PCM fuels. So pressure would be good thing to check.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I checked for vac leaks and I have aprox 20 in mG I have not checked the fuel pressure yet because I finally got my fuel pressure gauge from my buddies house last night. I was just messing with the truck and noticed that when I advance the timing it seems to run better with the map connected but not fully. Then I run out of turning room on the dist. Then it dies. Im now starting to think this is some kind of timing problem.?
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