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Discussion Starter #1
1998 chevy k1500 5.7... long block swap, new water pump, new plugs wires distb. cap and rotor. upgraded the CFI injection to MFI. Everything is back in place, it turns over and fires a little, idles for about 3 seconds (very roughly) but wont stay running. Doesnt run long enough to set a code. Has fuel pressure, has spark, timing has been set with Rotor pointed at #1 cylinder on compression stroke. I've checked the wiring and sensor for and replaced the crank position sensor, it was good. Checked all the grounds, seem to be all hooked up. Still does the same thing. Cant get a code to even get a starting point...any ideas anyone????
 

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How long did the truck sit waiting for the new engine?

Has the gas been in the truck for any length of time, or is it, like the engine, new?

Try some starting fluid sprayed into the throttle body.
 

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The trucks been sitting for a month or so, but that wasnt unusual for the truck, so dont think its a fuel thing....it fires with starting fluid but still just fires now and then...strikes me a a timing thing but I've gone back and set it up (distributor and rotor on TDC #1)about 4 times to check if I got it right. Anothre thought is that a sensor somewhere is bad or not sending a signal to the coil or something
 

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A basic spark checker/timing light should be able to tell if spark is present, intermittent, or non-existent. You say that it has fuel pressure, but no indication of how much pressure. I don't know how sensitive the upgraded injectors are to low pressure, but I know that the original style of injector was very sensitive to low pressure. I would probably also do something to check that injectors are firing to let fuel into the cylinder. Good pressure means nothing if the injectors are not firing.
 

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Discussion Starter #5
It has spark, used a tester...From what I've read the MFI can get by on less pressure than that CFI...but have around 55lbs, I've taken the upper plastic manifold off just to check if I had the injectors in the correct cylinder...pulled the plugs and they were wet with gas and since they were new I could tell they were sparking too...all this make me think of timing but cant figure where to go from here
 

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Are the oxygen sensors disconnected ? Can you get the engine to run to set any codes ? I know you said no,
 

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Discussion Starter #7
Everything I can find is plugged back in...been through the wires several times, top and bottom, cant find anything disconnected. Still wonder if some sensor somewhere isnt bad, but all sensors came off a running motor. Seems like timing to me...ordered a new distributor, be here tomorrow...see if that does something
 

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OK, I was thinking that if the O2 sensors are disconnected, the engine would have one less entray for the ECM to contend with. Sure it would set a code, but right now you need to get the engine running long enough to find the running problem.
 

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Usually when sensors are disconnected/broken, the computer uses a programmed value to replace the live data value. The engine usually starts; but sets a code.
 

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My dad's did that after we took to cover off to clean the throttle body and put in a new air filter. Finally figured out the plastic cover and plumbing for the air cleaner and throttle body were positioned exactly right, and some kind of sensor knew that and engaged what was effectively a fuel pump disarm system. It would crank, get gasoline for few seconds, and then the computer shut down the fuel pump. We re-positioned the plastic ductwork and it all worked fine.
 

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Discussion Starter #11
Got it going!!!! Installed an entire distributor, cap rotor and all....set it up exactly the way as the old one...fired up first time...dont know what was different.
 
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