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1976 Ranchero GT
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1,455 Posts
Discussion Starter #1
Hey guys I am looking for some advice on this 98 yukon. Its my sisters and she needs me to fix it. It was running one day and the next day no start. The motor turns over fine and will kind of pop or mis but no start. I dont know where to start with this dang computer controlled thing. Can I rent a scanner to check the computer? She is wanting to sell me this thing for fairly cheap and I like the fact that it has a vortec 350 but dang! What can I do? There was a lot of moisture under the hood and the ECM is under there as well I believe but it should not be affected by moisture right? :pain:
Also the check engine light had been on for a while and when I told her to get that checked out she said (I don't have time!) So you will have time when it brakes down on you? :spank:
 

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When you turn the key to the run position, you should be able to hear the fuel pump cycle.


Fuel pressure should be 60-66 psi with the key on engine off, or about 56 psi at idle.


You need to get the codes read with a code reader. ANy garage has these, they will charge you a diagnostic fee.
Or you can buy your own for $80 at any auto parts shop.

It could be 1 of many things, you need to know what the codes are.

Sounds like the truck needs some attention. MAybe cap, rotor, wires, air filter, fuel filter, plugs.

Teh Vortec 350's are excellent engines. Intake gaskets, injection system and fuel pumps are problematic in these trucks.

peace
Hog
 

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1976 Ranchero GT
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1,455 Posts
Discussion Starter #3
Yeah I guess I will save money in the long run if I just buy the scanner. I thought they were $400 but I just turned over my new JC Whitney and their is a actron obd-ll can scanner for $99. I guess every tool box could use one of these. The fuel pump was running. I did not check the pressure. I am hoping that moisture got under the old worn distributer cap and thats all. Not a bad ECM or intake gasket. :rolleyes: Thanks Hogg. ;)
 

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Yeah if you buy that $99 scanner, it will pay for itself after you use it once. Some dealerships are charging 1 hour at the shop rate for diagnostics.

peace
Hog
 

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Hotrodders.com Moderator
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Making noise does not meen the pump is pumping. Those are very picky about presure, less than 55 lbs and they wont run.
You did say it is popping so it also could be electrical but I would check the pump presure first. When is the last time the fuel filter was changed. These will also cause a no start if they restrict the flow enough.
 

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1976 Ranchero GT
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1,455 Posts
Discussion Starter #6
She had the fuel filter done not to long ago, BUT she had it done at a (quick lube) place so that does not mean it was really replaced. Funny thing is she rolled up to 200.000 miles just the day before it quit. ;)
 

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Save a horse, Ride a Cowboy.
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Since it is popping and trying(?).......If it is a cap and rotor system and there is lots of moisture, I would remove the cap and spray it well with WD-40, reinstall and spray the entire ignition system with WD 40 also. This will temporarily stop a crossfire.

Lots of people wash engines and the corrosion starts in connections, only to be a serious problem months later.

Scanner? Right. Most diagnosis cost $ 60.

I wouldn't trust JC Whitney. Buy one locally, so if it messed up out of the box at least you can get another one in less than 6 months.

Auto Zone or O'Reilly's might have a scanner at their stores that they will use to check your vehicle for you. :thumbup:
 

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1976 Ranchero GT
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1,455 Posts
Discussion Starter #8
Yeah I was going to try the old WD (water displacement) 40 trick but the distributer is buried way back pretty good. I will just replace the cap and rotor While I have it torn apart. I ordered the scanner from JC Whitney already after seeing that it was $50 more at the local parts place. Like you say That might come back to bight me. :nono: I hope this Yukon is OBD-ll compliant. :confused: This engine did at one time get the standard detailers engine degrease/ clean and armorall treatment so I will grease all the electrical connections with dielectric grease while I am under the hood. Thanks! :thumbup:
 

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I had one do the same thing, ended up being a crankshaft position sensor. Not saying that's it, but if its easy to get to maybe check it with a resistance tester-

K
 

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1976 Ranchero GT
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1,455 Posts
Discussion Starter #10
Crank position sensor sounds expensive. I guess I will see what my new scanner says. I am hoping it comes before the weekend. :drool: I love buying new tools! :sweat:
 

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Hotrodders.com Moderator
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killerformula said:
I had one do the same thing, ended up being a crankshaft position sensor. Not saying that's it, but if its easy to get to maybe check it with a resistance tester-

K
A good reistance check does not meen it is working. If it falls apart inside the coil could still be ok but re-positioned so it doesnt work. I got burnt by this once and it wont happen again. If it reads open however you can be fairly sure it is bad.
Sometimes in teh long run it is cheaper to find a good mechanic with a scope to see what signal is missing and let them fix it. Throwing parts at it can get real expensive.
 
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