Strange truck engine behavior - The 1947 - Present Chevrolet & GMC Truck Message Board Network

73 C-20 LWB · 12-26-2003, 11:27 PM

Today I was leaving the recycling center and the truck died...started right back up then on the way home the rpms dropped about 500 all of a sudden. I exited and got gas thinking it was low enough that it might cause problems. I checked the carb and it looked fine. Got back in and restarted and while idling it dropped 500 rpms again twice in a row real quick. Then it evened back out at 950 (normal). I came on home to post this and find out what could be causing it. On the highway there was a loud ticking like a lifter, but different sounding and it quit when the idle evened out again. Could it be the fuel pump getting ready to go?

The carb has a new fuel filter so I don't think that's it and the cap and rotor on the distributor are new.

What else could cause this?

Sweet72 · 12-26-2003, 11:44 PM

Sounds like an ignition problem. Maybe a plug wire or coil wire shorting and causing the ticking noise?
-Sam

**old Rusty C10** · 12-26-2003, 11:55 PM

make sure your iggy wires arent arcing out sometimes they hit exhaust manifolds or cross and do that . check that nothing is arcing int he cap and the rotor

Mike76251 · 12-27-2003, 12:24 AM

Fuel pumps will click pretty loud before they give up sometimes.
I had this happen to me a few years ago.
It started clicking and sounded just like a rod bolt was going or something for 5 or so days before it finally died.

73 C-20 LWB · 12-27-2003, 07:32 PM

I checked the wires and coil wire as well as the lead to the starter and found nothing out of whack. Started the truck again fine and it ran for several minutes, then dipped for a second and ran fine for several more minutes. I am afraid to drive it anywhere for fear that I'll get stranded.

Could it be a bad coil? Could it be a bad fuel pump? What kind of tests can I do in the driveway tomorrow to find out which one it is?

**old Rusty C10** · 12-27-2003, 08:37 PM

well if its ticking id leave the hood open and see if ya can pin it down when its idling. you can stick a long extension down and touch the fuel pump and put the other end by your ear to hear if the tick is coming from there
if its electrical id really expect to see something arcing if you hear a tick
if it needs t be under load carefully block it good and set the Emergency break and put it in drive but make sure it it rolls it wont roll into traffic or anything see what happens

73 C-20 LWB · 12-27-2003, 09:16 PM

It only ticked that one time and today made no noise whatsoever. I'll have to have help to put it under a load as I live on a hill and blocking won't work...it'll wind up in the park!

12-26-2003, 11:27 PM	#1
73 C-20 LWB Buffalo Elk Join Date: Dec 2003 Location: Dallas Posts: 50	Strange truck engine behavior Today I was leaving the recycling center and the truck died...started right back up then on the way home the rpms dropped about 500 all of a sudden. I exited and got gas thinking it was low enough that it might cause problems. I checked the carb and it looked fine. Got back in and restarted and while idling it dropped 500 rpms again twice in a row real quick. Then it evened back out at 950 (normal). I came on home to post this and find out what could be causing it. On the highway there was a loud ticking like a lifter, but different sounding and it quit when the idle evened out again. Could it be the fuel pump getting ready to go? The carb has a new fuel filter so I don't think that's it and the cap and rotor on the distributor are new. What else could cause this? __________________ Kelly C. Hanna Hanna Woodworks

12-26-2003, 11:44 PM	#2
Sweet72 Registered User Join Date: Nov 2003 Location: Alexandria, VA Posts: 1,534	Sounds like an ignition problem. Maybe a plug wire or coil wire shorting and causing the ticking noise? -Sam __________________ '72 GMC SWB C1500 Custom, frame-off in progress. 383 SBC, 9:1CR, Comp Cams XE262H, Scat internal balanced crank, Eagle SIR 6" rods, Keith Black dish pistons, Dart Iron Eagle 72/180 heads, Weiand Stealth intake, Stewart stage I water pump, Holley 4bbl vac sec, TH350 with B&M Shift Improver Kit. 12 bolt positraction.

12-26-2003, 11:55 PM	#3
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	make sure your iggy wires arent arcing out sometimes they hit exhaust manifolds or cross and do that . check that nothing is arcing int he cap and the rotor __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

12-27-2003, 07:32 PM	#5
73 C-20 LWB Buffalo Elk Join Date: Dec 2003 Location: Dallas Posts: 50	I checked the wires and coil wire as well as the lead to the starter and found nothing out of whack. Started the truck again fine and it ran for several minutes, then dipped for a second and ran fine for several more minutes. I am afraid to drive it anywhere for fear that I'll get stranded. Could it be a bad coil? Could it be a bad fuel pump? What kind of tests can I do in the driveway tomorrow to find out which one it is? __________________ Kelly C. Hanna Hanna Woodworks

12-27-2003, 08:37 PM	#6
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	well if its ticking id leave the hood open and see if ya can pin it down when its idling. you can stick a long extension down and touch the fuel pump and put the other end by your ear to hear if the tick is coming from there if its electrical id really expect to see something arcing if you hear a tick if it needs t be under load carefully block it good and set the Emergency break and put it in drive but make sure it it rolls it wont roll into traffic or anything see what happens __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

12-27-2003, 12:24 AM	#4
Mike76251 Senior Member Join Date: Mar 2003 Posts: 2,499	Fuel pumps will click pretty loud before they give up sometimes. I had this happen to me a few years ago. It started clicking and sounded just like a rod bolt was going or something for 5 or so days before it finally died.

12-27-2003, 09:16 PM	#7
73 C-20 LWB Buffalo Elk Join Date: Dec 2003 Location: Dallas Posts: 50	It only ticked that one time and today made no noise whatsoever. I'll have to have help to put it under a load as I live on a hill and blocking won't work...it'll wind up in the park! __________________ Kelly C. Hanna Hanna Woodworks

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