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98 gmc vortec motor

853 views 2 replies 3 participants last post by  LATECH 
#1 ·
i have a 98 gmc truck the motor stopped pumping oil to lifters and making loud noise i replaced motor and then the truck would not stay running at all i had mechanic come hook it up on machine it read back security he tells me its going cost alot money to fix it i did some reading that night and came across the 98 gmc have vats security box i replace it next day and the truck starts and security light went off and stays off but check engine light still stays on it has always been on never goes off all of and not to mention first motor and second motor both always missing and fouling spark plug 1 and 8 then my truck will not even start due to my fuel pump wont kick on at all i go and get different brain and vats box and replace it and chip on the ignition the truck starts and seems to be alot better but has still some missing but it is to where i can drive it down the road my second test drive it starts missing and cutting out and it dies i try start it and nothing it wont start it would not crank it was like battery dead but its not and i lost oil pressure it dropped to 30 and truck wont start this is second motor
 
#2 ·
That engine runs at 60-66 psi of fuel pressure.

VATS will allows the engine to run for 4 seconds, then will cause it to shut off as it shuts off injector pulsewidths.

Here are all the relearn procedures, follow the PAsslock if your key does NOT have a resistor in it.
http://www.bsecorp.com/files/techtips/ST9303l.pdf

Since this is your 2nd engine, by now you've realized that the engine isn't the issue here.

Sounds like you need a new CSFI spider (central port Sequential Fuel Injection) unit, or if you aren't making at least 58 psi of fuel pressure all the time.
You could also need a new distributer, get one of the cheaper $60 units that actually has a metal base rather than the stock plastic bodies distributer base.

Here is some distributer options
Then at Amazon, this $44 distributer pops up for our Vortec L30/3129 SBC and BBC engines.

https://www.amazon.com/Distributor-C...vrolet:c1500


It has the distributer screws hat are screwing into a metal body, not plastic like the stockers.
This also has a metal body for $69
https://www.amazon.com/dp/B01N2VPII9?psc=1

and this one for $59 Top Street Performance JM6672BK Vortec Distributor
https://www.amazon.com/dp/B006CUWF8C?psc=1

Up here I cant even get a Delco cap and rotor set for the price of these distributers.

EDIT I just found the MSD 5092 MSD Ignition 5592 Street Fire Distributor for GM Vortec V8 Engine for $238. Is the extra money worth it?
https://www.amazon.com/MSD-Ignition-...&keywords=5592


If your fuel pump wont run WHILE YOU ARE CRANKING THE ENGINE, then you have found youyr problem. The fuel pump MUST run while cranking as the engine requires 58+psi to run.
Try hitting your fuel tank with a rubber mallet WHILE you have someone else crank the engine over. If this works, then 100% you have a bad fuel pump. Banging on the tank causes the worn brushes of the electric fuel pump to work for a short time. Gets you out of a tow bill, but don't rely on this trick to keep you running, its a short term "get you home" type of deal.

Another way to see if your fuel pump and its associated wiring and control systems are functioning, is to turn the key to the run position, turn off the headlights, heater fan motor/interior lights so you don't deaden you battery. Then crawl underneath the truck and grab the torsional damper on the front of the crank, and then turn the engine over, if your fuel system, is working, turning the engine over will all of a sudden cause the fuel pump to cycle for 2 seconds. Obviously don't have any kids in the cab of the truck while you do this because if they hit the key, you'll get your hands caught up in the engine.
The engine must also make oil pressure in order for the fuel pump to run beyond the 2 second "fuel system purge" that you cause when you turn the crankshaft over.

These distributers can be a little tricky to stab correctly. But you've had it started, so you have to be close. In order to have the camshaft position sensor retard set properly, it must be at plus or minus 2º. This has nothing to do with ignition timing advance, its a fine correlation between the camshaft and crankshaft sensors.

This thread shows us a way to set the CMP retard in a cheap manner.
Vortec Cam Retard "Live" Check for $20

In fact, you should register at that forum as it deals directly with GMT400 trucks (1988-99) and more specifically the 1996-99 Vortec trucks.

GM Truck Central Forums


You have to be careful as you may now have a cylinder full of fuel causing your engine to not crank over. If you really think that your starter is working, and your battery is not dead I'd pop out the plugs and then try and crank the engine over, if there is a bunch of fuel that comes out and allows your engine to crank, then you for sure have a fuel delivery issue, most likely a spider issue or maybe a fuel pressure regulator issue.
Be sure your battery connections are tight, give the cables a wiggle, but don't overtighten the battery connections as you can damage the battery if the battery connection bolt bottoms out in the battery.

Sorry for the novel here, but your issues could literally be anything. A code reader that merely reads out codes isn't really of much help here, getting the actual sensor data from a true scan tool would help more, if you can get the engine running. Its really hard to diagnose over the internet.

Good luck

peace
Hog
 
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