1988 Sierra: every now and then motor won't start

[RayInAlaska]

I have the following problem with my 1988 Sierra GMC, 350 TBI motor, with a 5-speed manual transmission:

Every now and then (maybe once every other week) when I turn the key the motor won't start. It acts as if there is no power whatsoever going to the starter. The only noise heard is from the fan, and the gages and warning lights as well as the interior lights (if I have the door open) turn on normaI. Even the headlights turn nice and bright if flip the switch. But the starter solenoid does not click nor makes any noise whatsoever. If I remove the key and let the truck sit there for 30 minutes or longer, then it starts as normal. The battery is good (passes a capacity/discharge test).

The problem may happen after I park the truck after driving for a while and the motor is warm, but it may also happen when the motor is cold a few hours later.
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I have thought that perhaps the clutch safety switch may be malfunctioning, or that the starter may be going bad. So a couple of days ago I replaced the easiest component, the safety switch, but the motor failed to start right after. I let it sit there for a couple of hours, and then it started without any problem.

Have you had a similar experience to mine with your truck? I am trying to isolate the malfunction to as fewer components as possible, and can't think of anything else that may cause this problem.

[droberson]

Although I haven't dealt with this specifically on one of these trucks, my Jeep was doing the same thing for a while. When the engine was cold, it would fire up every time. Drive for about 15 minutes and try to start it again, no dice. Sometimes it worked, sometimes it didn't. It turned out to be the neutral safety switch.

When it wont start normally, can you short the starter out to start the engine? That might rule out the starter for you at least.

[RayInAlaska]

Originally Posted by droberson

Although I haven't dealt with this specifically on one of these trucks, my Jeep was doing the same thing for a while. When the engine was cold, it would fire up every time. Drive for about 15 minutes and try to start it again, no dice. Sometimes it worked, sometimes it didn't. It turned out to be the neutral safety switch.

When it wont start normally, can you short the starter out to start the engine? That might rule out the starter for you at least.

This truck has a clutch safety switch instead of a neutral one on the transmission. Haven't started it at the starter because there isn't enough room to start it that way, and there is not a starter solenoid in the engine bay like on older F-150 trucks. I still can wait a few days to see if it happens again. At least I can park it on a slight incline whenever I can, since I can roll-start it.

[droberson]

Bummer. I hope you figure it out!

[Palf70Step]

2 things come to mind. Starter/solenoid is heat soaked...if it does it mainly after running it a while. Could be the switch on the clutch is going out or being interfered with. My buddy's Mitsubishi had a piece of the carpet that kept the clutch from fulling depressing and engaging the safety switch. Once he permanently shift the carpet of the the way, no more start issue

[RayInAlaska]

Originally Posted by Palf70Step

2 things come to mind. Starter/solenoid is heat soaked...if it does it mainly after running it a while. Could be the switch on the clutch is going out or being interfered with. My buddy's Mitsubishi had a piece of the carpet that kept the clutch from fulling depressing and engaging the safety switch. Once he permanently shift the carpet of the the way, no more start issue

Hmmm...that crossed my mind before (switch interference by the carpet or something else), but I forgot about it. I will have to check that out since it is a good possibility.

By the way, a mechanic I know told me that sometimes the starter starts to "heat-lock" (whatever that means), which sounds similar to what you are saying.

I forgot to mention something else that may be important. When the motor failed to start (before I replaced the clutch safety switch), the starter would not make any noise (no clicks no chatter from the solenoid, nothing). But when I turned the key to start the motor, right after replacing the switch, I heard the solenoid chattering (the clicking noise heard when the solenoid is malfunctioning, or when the battery power is low).

I roll-started the truck, let the motor run for about 20 minutes at 1,100 RPM to make sure the battery was charged (the temperature outside was around 10 degrees, so the RPM stayed up for a while). Anyway, the following day (Sunday) the motor started without any problem, and today it was the same. I will probably have to wait a few more days to see if it happens again.

[dieseldawg142]

my daily is a '90 sierra k1500 with a 350/5 spd.
just went threw pretty much everything you have. i even tried taking the kill switch off my clutch interlock, no diff.
change your starter. they ARE a heat sink. i would have to wait to start it after it was warm. sometimes nothing, sometimes could'nt spin the motor fast enough to start. you must know what a pia that is when you have to fuel up (unless you have a gas station on a hill).
even with the factory heat shield, i was surprised just how hot it was getting when i touched it.
make your life way easier & swap it out with a mini starter. dont get near as hot & slides right in past the clutch line like nothing. you will need the bolts too. under a hundred for the starter & bolts, much better than always looking for hills to park on....


yeah, i was skeptical this thing would even start the truck, 1/3 the weight & half as small, 4 months on & a piece of mind she'll start when i shut it off....

[RayInAlaska]

Originally Posted by dieseldawg142

my daily is a '90 sierra k1500 with a 350/5 spd.
just went threw pretty much everything you have. i even tried taking the kill switch off my clutch interlock, no diff.
change your starter. they ARE a heat sink. i would have to wait to start it after it was warm. sometimes nothing, sometimes could'nt spin the motor fast enough to start. you must know what a pia that is when you have to fuel up (unless you have a gas station on a hill).
even with the factory heat shield, i was surprised just how hot it was getting when i touched it.
make your life way easier & swap it out with a mini starter. dont get near as hot & slides right in past the clutch line like nothing. you will need the bolts too. under a hundred for the starter & bolts, much better than always looking for hills to park on....
Attachment 1317709Attachment 1317710

yeah, i was skeptical this thing would even start the truck, 1/3 the weight & half as small, 4 months on & a piece of mind she'll start when i shut it off....

Thanks for your comments and photos. That has helped me a lot.

You are right about having to park on hills to roll-start. It gets old pretty fast, and worst as winter sets in.

I had no idea that there were mini starters like the one in your photo. I will check around, since we have NAPA, AutoZone, O'Reilly (?). Will ask all of them to see who has a small starter like that, because the one on the motor now is a monster

[dieseldawg142]

i've had zero problems starting since i put the mini in. just for comparison i threw both starters on the bathroom scale, the mini was a svelte 7 lbs, while the old one clocked out at 26 lbs. BIG difference when your upside down holding it over your head...
it's a bosch starter, designed to replace the big old starters, it came with the proper bolts for the change too. if i can find the receipt i can give you a part # if you want. nice thing too, should never have to buy another starter, life time warranty. good thing, in 18 yrs of ownership this is my 3rd starter.
and yes, i have had the carpet/floor mat catching under the clutch, check out the top corner of the floor mat...

[dieseldawg142]

well bummer, looks like i dont have a lifetime warranty unless i can find the receipt.
here's the part number for it. look at the room-ahhh! first time i changed the starter, bent the clutch line carefully out of the way... second time, carefully broke the clutch line... disconnected it this time....no more of that, from a real crappy job to a 10 min affair now. even if it only lasts as long as the other ones, the ease of future removal is worth it

[RayInAlaska]

Very good pictures, dieseldawg142

I appreciate all of that. I downloaded the photo and printed it so I can keep the starter model and part number.

By the way, I ended buying a set of Husky "molded" floor mats for my truck since we get a lot of snow on this side of the pond (the snow melts and creates a mess). Anyway, the floor mats fit like a glove, and the elevated edges prevent any moisture from spilling over.