@ZooMad75 I finally got around to checking fuel pressure. Sorta interesting find, the pressure drops FAST after I shut the truck off.
View attachment PXL_20230811_013429047.mp4
CK5
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1989 K5 - Gradual Learning
- Thread starter shima
- Start date
First 4x4 - learning basic maintenance / upkeep and maybe some small mods.
@ZooMad75 I finally got around to checking fuel pressure. Sorta interesting find, the pressure drops FAST after I shut the truck off.
View attachment PXL_20230811_013429047.mp4
I know that this tube with the wires going thru it is supposed to bolt up to the two bell housing bolts I'm pointing at. The wires that run through it feel pretty tight and I'm not sure how they will go through it without having to be rerouted. Does anybody have a picture of this on their truck they could share?
Those wires had/have a factory heat cover in that tube.
It gets hard and conforms to that shape.
Thop of tube to second up bell housing bolt bottom of tube goes on solenoid screw.
It gets hard and conforms to that shape.
Thop of tube to second up bell housing bolt bottom of tube goes on solenoid screw.
Check valve in pump or sending unit is no good
Yeah, mine used to do that, so I had to turn the key to prime a few times before starting. I even set the ECU to prime for 5 seconds instead of 2 (This is not a factory ECU). After I replaced the fuel pump it held pressure normally.
Agreed. Most likely issue is the check valve in the pump letting pressure bleed off. Though a leaky injector will cause the same drop in pressure. Though that’s pretty easy to see if that’s happening. Just pop the lid off the air cleaner and watch after the key is shut off.
Though I think a leaky injector is less common for sure.
Though I think a leaky injector is less common for sure.
While it is good to know, I wouldn't think (?) that the pump having a bad check valve (or leaky injectors) could cause the Blazer to stumble and eventually die (while in gear at a stop). Do you all agree?
That's the main problem I'm trying to solve, so if it is a separate thing then I'll ignore it until after Blazer Bash!
That's the main problem I'm trying to solve, so if it is a separate thing then I'll ignore it until after Blazer Bash!
What’s the fuel pressure doing with it running? Memory tells me spec is 12-15psi.
Running on the lesser side of the scale could make it stumble at idle because it’s running out of fuel.
Though if the fuel pump is weak you’d have more of an issue under acceleration when fuel demand is higher, not at idle or coasting down.
Running on the lesser side of the scale could make it stumble at idle because it’s running out of fuel.
Though if the fuel pump is weak you’d have more of an issue under acceleration when fuel demand is higher, not at idle or coasting down.
Let's say an injector is never quite closed all the way (maybe ethanol deposits or something). That might not be enough gas to effect higher RPM/load conditions while still making it rich at idle. With no quantitative basis, it seems like the gauge is dropping too quickly for that to be the only issue. The ECM can adjust for weird injectors, to an extent. Again, it should be obvious if fuel is dripping with the engine off.
I'll pull the air cleaner tonight and check whether it's dripping down after I shut the truck off. I also want to pull the plugs just to see what they can tell me.
@ZooMad75 it was pegged at 13 psi while it was running. I was kind of hoping to test the pressure without the fuel filter in line to see whether the filter is clogged up. It is only 10k miles old but it is a cheapy AutoZone filter. Who knows.
@ZooMad75 it was pegged at 13 psi while it was running. I was kind of hoping to test the pressure without the fuel filter in line to see whether the filter is clogged up. It is only 10k miles old but it is a cheapy AutoZone filter. Who knows.
I couldn't see any dripping from my injectors after I shut off the Blazer.
I pulled the plugs last night as well... do these look a little lean to you guys? Sorry that the first pic is upside down.
I'm not an expert plug reader, but none of those would freak me out by any means.
I wish mine would come out that nice looking. Those are clean.
They have just enough tan, for today's fuels.
I'd run them.
I went out and played with the Tech 1 scan tool yesterday. A guy on reddit sent me this link that shows expected values for a lot of the various things the Tech 1 shows. I fired up the Blazer, let it warm up, and tested it while it was in Park.
Here are some of the readings I pulled. The bolded items are out of spec with the link the guy gave me.
I shut off the Blazer after doing this test and it would not fire up again. I think that the IAC was completely closed because the only way to keep the Blazer alive was to have my foot on the gas. I had to disconnect the battery for a while and hook everything back up again for it to start. I did a second test and here are the readings...
http://www.gearhead-efi.com/Fuel-In...?62-Initial-Set-up-of-throttle-blades-and-TPS
I think I am going to try going through the steps on that post and see how the Blazer's behavior changes.
Here are some of the readings I pulled. The bolded items are out of spec with the link the guy gave me.
- Engine Speed: 1000 RPM (This seems crazy high)
- Coolant Temp: 187F
- MAP: 0.94V - 1V
- 02: 0.4mV - 750mV
- IAC: 12
- Park/Neutral: R-D-L (While in Park)
- INT:132
- Block Learn: 117
- Open / Closed: Closed Lp
- TPS: Started at 0.7V, then settled down to 0.74V, 0.74V, 0.8V after I hit the throttle and released a few times.
I shut off the Blazer after doing this test and it would not fire up again. I think that the IAC was completely closed because the only way to keep the Blazer alive was to have my foot on the gas. I had to disconnect the battery for a while and hook everything back up again for it to start. I did a second test and here are the readings...
- Engine Speed: 1000 RPM
- Coolant Temp: 189 F
- MAP: 0.88 V
- 02: 0.4 mV - 750 mV
- IAC: 61
- Open / Closed: Closed Lp
- Park / Neutral: P-N--
- Int: 128
- Block Learn: 128
- TPS: 0.6 V
http://www.gearhead-efi.com/Fuel-In...?62-Initial-Set-up-of-throttle-blades-and-TPS
I think I am going to try going through the steps on that post and see how the Blazer's behavior changes.
The o2 reading is supposed to fluctuate above n below .05v and do so many times a minute.
Map reading is manifold vacuum. Could be vacuum leak or condition of engine.
I started the IAC reset procedure and my IAC connector is making a wild buzzing noise. The whole thing is vibrating. This is after connecting the A and B terminals and turning on my ignition (but not starting the engine).
I think there could be legs on this "minimum air" thing. My engine absolutely won't run with the IAC disconnected and this Eagle Mark thread implies that it should be able to do so.
EDIT: Now I'm finding threads that confirm the plates should be fully closed at idle. Given that GM blocked this torx, I'm guessing that's right. Ugh.
EDIT: Now I'm finding threads that confirm the plates should be fully closed at idle. Given that GM blocked this torx, I'm guessing that's right. Ugh.
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