- This topic has 8 replies, 3 voices, and was last updated 9 years, 4 months ago by
.
-
Topic
-
Hello again guys. I have currently having an issue with the 1995 Chevy K1500 truck. I just got done swapping out the motor with a low mileage one that i saw running before I pulled it. I swapped out the motor because the old one had some main bearing clearance issues (but that is besides the point). After hooking everything back up, I went to the moment of truth and cranked the engine over. All I got was the dreaded sound of the engine cranking…. I started looking things over and found that there was no fuel spraying out of either of the injectors.
Here is what I did so far:
-checked all plug wires and firing order (I didnt remove the distributor in-between when I pulled it and dropped it in)
-checked spark – Good spark
-checked the fuel pump to make sure it was priming – it was
-I did not check to see if fuel was present because it was getting dark and I did not want to be cracking fuel lines next to a light, but I have a new fuel filter sitting on the shelf I havent gotten to installing yet, so i will check it there tomorrow.
-checked all of the connections making sure everything engine wise was plugged in (I have offroad lights and other items that I havent connected yet)
-Checked that 12v is going to the injectors. going to check the pulsing on the injectors tomorrow when i have a helper to crank the engine while I check it.
-checked all fusesHere are things I have noticed:
-oil pressure gauge builds to around 20-30 psi when cranking (before this engine was pulled it would be a steady 60 psi cold 40 hot)
-tac does not move (bad crank position sensor?)
-the engine cranks over a little fast, but i think that is just the high torque started that is on the truck. It sounds like it has good compression
-the spark wire going from ignition box? to the distributor did not fit when I installed MSD wires. But it could be I have ordered the wrong kit. I currently have the old wire back on right now.I have a 100 dollar bet that I drive this truck to work the week of july 27th, and it still needs to go to the exhaust shop before then, so any help is welcomed and appreciated. If you are needing any pictures or videos to help us diagnose this, I will be more that happy to get those uploaded as fast as I can.
Thanks
-
Replies
-
You need fuel, air/compression, and spark to make the engine run. Make sure all of those are present. The injectors will not fire if the crank position sensor is bad or poorly connected. You would still get a tach signal if the fuel filter or spark wire was bad, so you can rule them out. Make sure all connectors are firmly seated and locked in place. They may ‘look’ connected, or even feel mechanically connected, when they aren’t actually electrically connected.
Im thinking its the two connections on the back side of the distributor. i plugged them in blind and I am not positive they are locked in.
What should the tac be reading when cranking? 600ish?
Cranking RPM depends on several factors, such as the ability of the starter, battery condition, wiring, and engine compression. I’ve seen as low as 50RPM. I’d say ~200-250 is probably about average. If you’re getting over 500RPM, you may want to run a compression test.
[quote=”husker240″ post=142770]Im thinking its the two connections on the back side of the distributor. i plugged them in blind and I am not positive they are locked in.[/quote]
This is most likely the cause since both the tach and injectors need to see the signal from the distributor to work.
Got the truck running!
However I notice when it is idling it will backfire on the passage side (2,4,6,8) and it seems to shake a decent amount. It is idling at 900ish rpm. (Not fully warmed up). And when I drop it in gear it goes down to 550-600 rpm and acts like it’s kinda bogging down. And shakes even worse. Is jumped the obd 1 and 2 terminals and only got a code 12.
I have notice that the new plug wires dont seem to fit too well on the distributor side. It seems like the rubber is too tall.
It was doing this, but not as bad when I pulled the motor. I figured back then it was it had just decided to spin a bearing.
Any ideas?
Sounds like an ignition issue.
Did you put dielectric grease or silicone paste on the inside of the spark wire boots (both ends)? If not, you really need to. Plus, it may help the wires seat themselves. If the spark wires aren’t seated properly and making good contact at either end (or both!), that can cause misfire.
Ok so I think I may have gotten it figured out. Its not misfiring, it was just some bad gas due to age, 5 months. I drained what was there and out 5 gallons of new gas in and it stopped shaking as much. It is almost the normal amount of shaking, but since I put new mounts on I figure that is where the rest is coming from.
As for the back fire, I think it is from this truck not having any o2 sensors (Previews owners right? You should see the rattle can this guy did it started chipping right after I bought it) so it is running in an open loop. Since it is open headers, it ignites right away. Where I think that once the exhaust is welded back on, it will stop back firing. the previous engine never back fired like this. Now my list has new headers and rewiring the o2 sensors on it.
A buddy of mine told me I should not worry about the back firing quite yet until the exhaust is back on and if it continues then I need to hurry up and get the o2 sensors installled
Thoughts?
after talking with summit for awhile, we finally got the backfire problem down to the msd wires not being compatible with the cap on my distributor. they are sending me a new set of wires from a different company and returning the msd ones. the technician said that this happens with some replacement caps because they are slightly off spec and dont allow the wire to make a good connection because of the boot being slightly too tall. I am running the stock wires right now and its running nicely. I have 20 lbs of oil pressure fully warmed up at idle. although it does seem to idle a little high (1,000 rpm) but i have not yet tested any sensors. to see if anything is bad (Ive got a gut feeling it might be the cts as the idle doesnt change from cold to hot)
and as a thank you for helping me with theses quirks, i have attached a couple images
- You must be logged in to reply to this topic.