1987 Burb TBI to carb swap

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RecklessWOT

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Joined
Feb 20, 2015
Posts
2,548
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Location
New Hampshire
First Name
Kevin
Truck Year
1987
Truck Model
V10 Suburban Silverado
Engine Size
350 TBI
Part of the FRIGGIN NUTS 700 was a new ECM. New ECM MAP SENSOR TPS (2) IAC (2) Temp sensors , O2 sensor. Nothing helped. Took to shop. He found bad pickup coil so put in NEW complete distributor he said he had for a small block on his shelf and sold me cheap as in 50$ but also rebuilt the TBI and regulator. Seemed fixed. Then the idle acted up again and threw code 42. He showed me the pickup coil though and it was toast.
SO in chasing the new code 42 being ignition module open or short of fuel relay circuit open or short. I replaced both items even though the ignition module in new distributor was new. His labor was factored in as well. He did good as always. Talking me out of the entire engine swap. Which I am not ruling out at this point. We will see.
I have had more TBI and other injections my last a 5.3 LS. But I have had my share of carbs over the years and have never had issues. My 69 firebird of course is stock and with a carb fires up pretty easy unless it sits for a week. Not typical but does happen.
Everyone on here talks about scrap yards for parts. None near me unless there are unknowns in the country are all 2005 and up if not 2010. Anything older they scrap to a shredder. Now I am working on the fuel tanks and entire fuel system. I figure when I get it started today if there are no leaks from water at the intake and it runs good I will most likely order two new 85 tanks and senders with no return lines, I will buy a complete new harness from nose to tail EVENTUALLY and if it we like it after 6 months I may go ahead and order a long block and these parts can swap over on it. At least by then all the sub systems are going to be in place and done. This will be a brand new old 87. OR it will be in someone else garage!
It is solid and we both like the truck. Underneath being I have been under it now for a week is solid as a rock as well. Surface rust on the frame but solid other than that. While it will not be off road it will be in fields maybe at times on the property. And while it will be sharp I will not be a show truck owner. I am not a stickler for stock only although my firebird is 95%. I like clean, no ugly nest of wires nice paint although nicks are okay. Will watch what I do but haul as I need. It will be getting a hitch. It is the truck in the picture but without the 20 inch the prev owner had on it. Like riding on bricks. Now it has coopers on stock rally's.
Even if your local yard doesn't carry the part, they're all in a network (unless it's some real auntie-mom-sister-wife type of place in which case you should stay away anyhow), any real salvage yard can easily trade and order parts in from other yards in the vicinity on a locator service. I have worked in some strictly late model only salvage yards over the year or ones that specialized in euro cars or whatever, but if some dude comes in looking for stuff for an old Chevy we could still get it for him. Not gonna be a pick your own part type of place (a lot of states don't even allow that anyway for insurance reasons anyway), but will still be cheaper than BRAND NEW stuff, I can only imagine how much that computer was jeez!

And I wasn't saying that's your problem necessarily, I was more just saying before you throw a grand at it to ultimately rip it all out anyway, your problem could very well be some stupid sh!t you overlooked that is an easy cheap fix. Has anyone actually hooked it up to an OBD diagnostic tool and got readings from all the sensors while it's running? A competent mechanic should be able to see what's off. Massive intermittent vacuum leak, loose electrical connection somewhere that intermittently cuts out, should be able to pick up on it if your buddy is someone who knows what to look for. I'd hate to see you throw a carb at it just to have the same exact problems, AND get worse fuel mileage and less horsepower, not to mention the hassle of trying to reliably start a carbed vehicle in colder weather or one that doesn't get driven often, etc. Hell, it's snowing out and I haven't moved the burb in months, but with that EFI there's no doubt in my mind I could twist the key and it would bark off in 3 seconds.

Also, I am glad to hear it's riding on rallyes now, hah I hope them coopers have some nice raised white letters! To each their own, but yeah man the wheels in the picture I personally wouldn't be seen driving around with
 

eric 87

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Joined
Aug 3, 2021
Posts
89
Reaction score
26
Location
Kentucky
First Name
Eric
Truck Year
1987
Truck Model
GMC Sierra Shortbed
Engine Size
305 tbi
Even if your local yard doesn't carry the part, they're all in a network (unless it's some real auntie-mom-sister-wife type of place in which case you should stay away anyhow), any real salvage yard can easily trade and order parts in from other yards in the vicinity on a locator service. I have worked in some strictly late model only salvage yards over the year or ones that specialized in euro cars or whatever, but if some dude comes in looking for stuff for an old Chevy we could still get it for him. Not gonna be a pick your own part type of place (a lot of states don't even allow that anyway for insurance reasons anyway), but will still be cheaper than BRAND NEW stuff, I can only imagine how much that computer was jeez!

And I wasn't saying that's your problem necessarily, I was more just saying before you throw a grand at it to ultimately rip it all out anyway, your problem could very well be some stupid sh!t you overlooked that is an easy cheap fix. Has anyone actually hooked it up to an OBD diagnostic tool and got readings from all the sensors while it's running? A competent mechanic should be able to see what's off. Massive intermittent vacuum leak, loose electrical connection somewhere that intermittently cuts out, should be able to pick up on it if your buddy is someone who knows what to look for. I'd hate to see you throw a carb at it just to have the same exact problems, AND get worse fuel mileage and less horsepower, not to mention the hassle of trying to reliably start a carbed vehicle in colder weather or one that doesn't get driven often, etc. Hell, it's snowing out and I haven't moved the burb in months, but with that EFI there's no doubt in my mind I could twist the key and it would bark off in 3 seconds.

Also, I am glad to hear it's riding on rallyes now, hah I hope them coopers have some nice raised white letters! To each their own, but yeah man the wheels in the picture I personally wouldn't be seen driving around with
The ECM was only about 120. And yes it sucked to toss out 700+/- on parts that are of no use now. I will list them on one of the facebook groups and be in no hurry to sell them. At least it didn't come out of grocery money. And the carb is on and it is starting/running. Haven't taken it down the road yet. Did a mod on throttle linkage screws. That vacuum servo linkage rod doesn't reach now by about an inch and not sure how loose that slot is to be on it/ adjustment. And now that the computer will be gone not thinking it will do much for cruise but that vacuum I believe also operates the heat and AC actuators in the cab from floor to vents etc. Trying to figure that out.
Have been researching if there is any wires from the ECM I need to keep. My only unsure is the neutral safety wire from the ECM I don't think I need with the th400 trans. Also the AC signal wire from the ecm and what its function is if needed or where they need to be hooked up.
Yep I tested not only the old but the new sensors for voltage signal to ohms. Each and everyone proved to be accurate and within their specs. After I exhausted what I knew to try my local shop guy put it on his laptop and found the pickup coil was bad. Even though the IAC said it was good by testing the idle was still fluctuating BADLY from quiting at traffic lights so low to so high it went down the road at a good 35 mph or better with 2500 rpm without giving throttle. All over the place. I picked it up after hours from the shop since they closed before we got off work and were able. This is when it began the dying routine on the way home. THen half throttle idle.
I will gladly give up a couple miles a gallon if it is dependable. Our highs this week for a few days will be 30 and lows in the teens. Now all three vehicles are in the garage but we will see. The choke and idle need adjusted a little bit but it fired up pretty easy. The electric choke seemed to work properly just needs adjustment.
If all goes well I intend on a new harness for an older model truck. I will put new older year sending units in tanks. Then I will decide or know by then if I am keeping it or not. If I do I will start on the minimal body work in sanding and paint it. Not sure I will keep it the stock color although I don't think it came the Pearl white it is in 87. It may go a nice blue or burnt orange. ALthough the charcoal and black interior would look better with the blue or a deep Candy wine color.
If I don't keep it I will just do the edge touch ups on the door edges by above the body line. Odd places for nicks.
So that is the long of it. The swap is done with some touch ups. I am using a holley low pressure inline pump and no return lines or regulator. Ran new lines and a new 3 port selector valve that is on only when I use right tank. When I flip the switch it goes off and reverts to the left tank. Thought about the relocation of tank to rear and have one tank but do not want filler in bed. I can see my wife driving the truck and needing gas reaching over the bed to open tank and get dirty if raining! That will go over like a lead balloon!
 

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