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Username Post: Hard start in colder months        (Topic#349445)
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-01-18 09:28 AM - Post#2722977    

I have an 89 Silverado with a 95 tbi with about 35k miles on it that starts almost immediately as you turn the key in the summer months but once it cools off around 45 and below the engine will crank and crank and crank for about 10 seconds before firing and immediately shut off. Then try again and a few seconds of cranking and it’ll start. Ive replaced and tested most sensors.
TPS tested smooth from closed to open
ECT-new
MAP-new
Knock-new
O2-new
Oil pressure sensor/sending unit-new
EGR-new
PCV-fine
Fuel pump relay-new
Fuel filter-new
Fuel pressure regulator-rebuilt
Distributor-new
Plugs/wires-new
I think the only thing I haven’t tested is fuel pressure as I don’t have the adaptor for the tbi, iac, electronic spark control and and vacuum. It’s runs and drives perfect once it starts and once the motors up to temp it fires up no problem. Fuel is consistent from the injectors in a nice perfect cone on each side and no dripping. I’ve been told that the fuel pump either works or doesn’t don’t know the truth behind that exactly. The only thing I find puzzling is that I cannot hear the fuel pump prime when you turn the key on. Everything’s stock on the truck other than the headers. It’s starts almost instantly with the coolant sensor unplugged when the motors cold also. Any advise would be much appreciated.



 
someotherguy 
Moderator
Posts: 28719
someotherguy
Age: 48
Loc: Texas
Reg: 08-01-03
02-01-18 11:12 AM - Post#2722986    
    In response to Biwman13

Welcome to Chevytalk,

The "pump either works or it doesn't" can be disproven as many of us have suffered driveability issues with marginal fuel pressure, and also pumps that go intermittent before totally failing. I don't believe this is your issue at all though, just wanted to clear up that notion.

Unlugging the ECT/CTS and having an immediate improvement in behavior sure does point to that sensor. Just because it's new doesn't mean it's good, especially if it's an off brand. There may also be excessive resistance in the circuit if the grounds for the sensors are in poor condition or the wiring is damaged anywhere. Check/clean/repair the grounds at, and next to, the thermostat housing. If the ECT/CTS is an off brand (especially if it's an Airtex, Bosch, etc.) consider replacing it with an AC Delco or Delphi piece.

That circuit works off resistance; the more it sees the colder it thinks the engine is, which will fatten up the fuel mixture. When you have really excessive resistance the mixture can be so rich the engine can fail to start completely (flooded, fuel-soaked spark plugs) or start and then stall due to flooding.

By the way the fitting for a pressure test gauge can be had for about $10 if you shop carefully; some places sell it for $30 and up. Or you can buy a pressure test kit with the fitting included. Again though I don't believe your issue is fuel pressure though it never hurts to know what it is.

Also don't worry too much about not hearing the pump prime unless you're used to hearing it on your particular truck. The TBI pumps are usually too quiet to hear them fire up unless you're in a closed garage with no ambient noise. The Vortec pumps are usually quite louder.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-01-18 11:59 AM - Post#2722990    
    In response to someotherguy

Too thank you! I’ll double check the grounds ASAP this weekend. I just thought it was strange when I unplugged it it started instantly. But I guess resistance could be the issue. Fingers crossed that’s all it is because I’m out of ideas. Do you know where to get that adaptor to test the fuel pressure for $10?



 
someotherguy 
Moderator
Posts: 28719
someotherguy
Age: 48
Loc: Texas
Reg: 08-01-03
02-01-18 12:07 PM - Post#2722991    
    In response to Biwman13

Actron used to supply this one with some of their kits, their price was $8 but is now $11 and says free shipping:

https://actron.com/content/gb-tbi-fuel-a dapter-12

How well it works across the board with various gauge kits, I really don't know; I use mine specifically with the Actron kit it came with - the CP7817, which appears to be discontinued. You can still find that kit for sale in various places; I just spotted it on Amazon for about $36 shipped which is a pretty decent deal for the whole thing.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
65_Impala 
Very Senior Member
Posts: 4049

Reg: 12-29-02
02-01-18 12:58 PM - Post#2722995    
    In response to Biwman13

Since you can't hear the pump prime try unplugging the oil pressure switch and see if the truck will still run. If it does run, then the fuel pump relay is working and powering the fuel pump. If the truck doesn't run then then the fuel pump relay is not working and the truck is running off the oil pressure switch. I don't really think it's the issue, but it's easy to check.

If you could get a scanner (or laptop with cable) on it then you can check what the sensors are reading before a start and know that the coolant temperature sensor circuit is working correctly. Otherwise, you're just hoping it's OK the same as you're hoping the fuel pressure is OK.



 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-02-18 09:03 AM - Post#2723067    
    In response to someotherguy

Thank you! I’ll snag one and give it a go and see what I come up with.



 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-02-18 09:04 AM - Post#2723068    
    In response to 65_Impala

Yes it does still run with the switch uplugged. You mean a to hook up to the obd1 port?



 
Sonny Baker 
Forum Newbie
Posts: 16

Reg: 12-21-17
02-02-18 05:17 PM - Post#2723125    
    In response to Biwman13

I see you replaced the distributor, did you replace the ICM as well?

If not, unhook the ESC wire at cold start.
If the engine starts and runs sluggish, but smooth, I would replace the ICM.

It could be that the ICM is not going into bypass mode.



 
CowboyTrukr 
"7th Year" Silver Supporting Member
Posts: 3989
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
02-02-18 06:38 PM - Post#2723139    
    In response to Sonny Baker

The ICM is integral to the distributor on the ‘89.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-03-18 05:59 AM - Post#2723173    
    In response to CowboyTrukr

  • CowboyTrukr Said:
The ICM is integral to the distributor on the ‘89.



Yes the dist came with a new ICM



 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-03-18 06:01 AM - Post#2723174    
    In response to Sonny Baker

  • Sonny Baker Said:
I see you replaced the distributor, did you replace the ICM as well?

If not, unhook the ESC wire at cold start.
If the engine starts and runs sluggish, but smooth, I would replace the ICM.

It could be that the ICM is not going into bypass mode.



Yes the dist came with a new ICM.



 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-03-18 08:40 AM - Post#2723183    
    In response to Sonny Baker

  • Sonny Baker Said:
I see you replaced the distributor, did you replace the ICM as well?

If not, unhook the ESC wire at cold start.
If the engine starts and runs sluggish, but smooth, I would replace the ICM.

It could be that the ICM is not going into bypass mode.



With the ESC disconnected there's no change in his it starts but almost seems to run smoother after initial start for about a minute or so.




 
Biwman13 
Forum Newbie
Posts: 9

Reg: 02-01-18
02-05-18 07:26 AM - Post#2723394    
    In response to Biwman13

I did notcir when I crank it cold the oil pressure is at 0. Not sure if this could be an issue or not. I swapped that oil pressure sensor twice already..



 
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