ls swap very hard cold start!
11-03-2019, 06:51 PM
#1
ls swap very hard cold start! Hey I have customer who called me out today to check out his ls swapped 57 Chevy Belair. He installed a 04 5.3/60e with a rebuilt stock harness tht he sent off to have done. The 04 Silverado donor vehicle ran perfect before engine pull. Car was having an issue where if it sits for a few days its very hard to start. Like take 10-20 tries to get it to run, It will sometimes hit and try and pop back etc. When it does finally start with throttle is stumbles like crazy. If u let it sit and warm completely up, it will hot start all day without any issues. The original tuner had some thing out of whack in the tune, so I retuned it. I've done a lot of swaps and have been tuning for yrs.
So with my tune I'm not sure if it cured the start up issue, the car had done warmed up by the time I tuned it and it seemed fine. Now here is some things I came up with tht wasn't right and wanted to get u guys opinions on it. I wish I could have originally swapped this car, it would have saved the owner and myself some headache. I hate going behind someone else!
Everything is stock besides the fuel rails and intake manifold. He is using a BBK SSI intake with Jegs billet fuel rails. He is also running a returnless fuel setup with a corvette regulator combo. Car has an intank fuel pump setup with stock flex fuel 33# injectors.
From what I saw he had the maf installed into the cai backwards. Im not sure If this would cause a cold start issue but I know I doesn't help the situation. I've never seen the symptoms of one installed backwards. Like I said I'm going behind someone elses work! The other thing with the car, is it has a hard stumble with a quick wot hit. Car takes a few seconds to recover thin opens up and runs. IF u ease into it, it doesn't bog nearly as bad. I'm thinking this is a fuel pressure issue.
So I checked under the car and he is using a vette regulator at the rear near the tank, thin 3ft afterwards he has another fuel filter like on an obs style truck. Thin it runs to the rails and deadheads out the rear. Now, could he having 2 5 micron filters hurt the fuel flow in this setup? I would think so. The owner didn't know the vette reg. had a built in filter, so he added the 2nd not knowing. What are your thoughts on this? any help is appreciated. I think im on the right track but I just wanna verifies to help with time and any more money on his part. He says this has been a long going money pit issue! Thanks guys!
So with my tune I'm not sure if it cured the start up issue, the car had done warmed up by the time I tuned it and it seemed fine. Now here is some things I came up with tht wasn't right and wanted to get u guys opinions on it. I wish I could have originally swapped this car, it would have saved the owner and myself some headache. I hate going behind someone else!
Everything is stock besides the fuel rails and intake manifold. He is using a BBK SSI intake with Jegs billet fuel rails. He is also running a returnless fuel setup with a corvette regulator combo. Car has an intank fuel pump setup with stock flex fuel 33# injectors.
From what I saw he had the maf installed into the cai backwards. Im not sure If this would cause a cold start issue but I know I doesn't help the situation. I've never seen the symptoms of one installed backwards. Like I said I'm going behind someone elses work! The other thing with the car, is it has a hard stumble with a quick wot hit. Car takes a few seconds to recover thin opens up and runs. IF u ease into it, it doesn't bog nearly as bad. I'm thinking this is a fuel pressure issue.
So I checked under the car and he is using a vette regulator at the rear near the tank, thin 3ft afterwards he has another fuel filter like on an obs style truck. Thin it runs to the rails and deadheads out the rear. Now, could he having 2 5 micron filters hurt the fuel flow in this setup? I would think so. The owner didn't know the vette reg. had a built in filter, so he added the 2nd not knowing. What are your thoughts on this? any help is appreciated. I think im on the right track but I just wanna verifies to help with time and any more money on his part. He says this has been a long going money pit issue! Thanks guys!
11-03-2019, 08:20 PM
#2
TECH Senior Member
Pull the 2nd filter and see what happens. I though the finer filter was 10 micron, not 5. 2 of those in series would be a restriction.
11-03-2019, 08:27 PM
#3
I was thinkin 5 but they could be 10. Yea i think imma tell him to pull tht off and see what happins. Definately no need in 2. I was just curious if anyone has ran a setup similar. What u think about the backwards maf?? He has had 2 mechanics look this thing over and neither have saw these 2 issues!
11-03-2019, 08:46 PM
#4
TECH Senior Member
There should be a mark or arrow indicating direction of airflow on the MAF. You sure it's on backwards??
11-03-2019, 09:34 PM
#6
Exactly. I thin the fuel filter is the issue with the bog at wot. The cold start issue i was leaning toward the backwards maf.
My understanding is when cold its in open loop. Once warm its in closed loop and maybe the o2s are helping it? This car is kinda crazy really. First time i have ever seen one act like this for a simple ls swap setup.
Ive personally done over 30 ls swaps and ive never had one act like this one.
My understanding is when cold its in open loop. Once warm its in closed loop and maybe the o2s are helping it? This car is kinda crazy really. First time i have ever seen one act like this for a simple ls swap setup.
Ive personally done over 30 ls swaps and ive never had one act like this one.
11-03-2019, 10:17 PM
#9
I connected hptuners to it and checked all tht. No codes and all data looked good. But when i first scanned it maf did read crazy low on hz (400-500 while cranking) Thin i got to messin with and noticed maf was backwards. Switched it around and car fired right up. But owner said we had messed with it enough to were it probably just started up lol. Car did run like crap and bogged when giving it gas.
So in theory i think the maf fixed the cold start issue, and the fuel filter is the fuel problem.
Owner is gonna let car sit till friday and give it a cold start try and see what happins. Hopefully the maf did the trick!!
So in theory i think the maf fixed the cold start issue, and the fuel filter is the fuel problem.
Owner is gonna let car sit till friday and give it a cold start try and see what happins. Hopefully the maf did the trick!!
11-03-2019, 11:05 PM
#10
TECH Fanatic
iTrader: (7)
IAT's and coolant temp were all in line with ambient temps on initial fire up when cold??
Meaning if the ambient temp is 50*, and your ECT reads much higher (180*-220*) he'll experience a noticeably lean condition until they equal out...
Meaning if the ambient temp is 50*, and your ECT reads much higher (180*-220*) he'll experience a noticeably lean condition until they equal out...
11-04-2019, 12:36 PM
#16
TECH Senior Member
Pressure key on means zilch. Pressure while REALLY Moving means mucho mas.
That's like checking a runner's heart before the marathon. It WILL be good. Check it at the finish line, WAY different story.
That's like checking a runner's heart before the marathon. It WILL be good. Check it at the finish line, WAY different story.
11-05-2019, 02:12 PM
#18
I recently had some dumb stuff with a p59 that would do something similar. i guess the engine segment got corrupted? I did an engine segment swap with a known good 7603 OS and it went away.
not sayin thats your problem (or problems) but its worth a look.
log prime pulse, cranking pulse, braf, iac and all that jazz. keep pokin at it and it'll eventually work.
and dont forget to charge by the hour, not by the job!
not sayin thats your problem (or problems) but its worth a look.
log prime pulse, cranking pulse, braf, iac and all that jazz. keep pokin at it and it'll eventually work.
and dont forget to charge by the hour, not by the job!
