1997 Chev Vortec - Replaced FI spider, now wont stay running more than 5-10 seconds...

10

Asked by Dec 13, 2015 at 11:51 AM about the 1997 Chevrolet C/K 1500

Question type: Maintenance & Repair

I have a 1997 Suburban 1500 4x4 w/Vortec 350.

Have had continual error codes for O2 sensors, Multiple Random Misfires, Mixture Too Lean, some others.

Was told probably had injector blocked, so did injector cleaners few times.

Now got to running very poorly - not all cylinders seemed to me.

So talked to few mechanics and told me time to replace the fuel spider to the upgrade Multiport FI. I bought the OEM Delphi unit.

FYI - Previously had replaced Fuel Pressure Regulator, and that helped instant start.

Opened up the upper manifold, and it was all carboned up inside cover - totally cleaned it.

Top of the lower manifold had wet black sludge all over it.
Cleaned it to as good as could be without making it a career,with paper towels soaked with carb and brake cleaner to breakup the cooked and wet sludge.

Got it pretty clean, including intake ports as far as I could reach in.

Took strong shop vac to all areas cleaned and into each intake port to make sure no pieces of paper towel residue left - cleaned as best I could.

Wire brushed FI port ridges in manifold, to clean all 8 of those.

Installed the fuel spider - the ends to the outer FI ports, the next rolled inner FI lines over the outer FI lines to the inner ports, per instructions.

Put everything back together, and was looking for motor to work like new, but it start sounding strong, but runs for 10-20 seconds and then dies.

I can get it to run a little longer by giving it more throttle, and then just dies, and did get a few back fires.

Looked over all connections and base installation of the upper manifold appears to be flat and sealed.

BTW - When I put in the FRP previously, I used a little HI Temp Copper RTV on the upper manifold base gasket, but did not do that this time...

Should I have, as I did before?

Parts store said no with rubber gasket...

Worked for me before with the FRP replacement fix about six months earlier.

I gave up last night, as it was late and thought I would see what you guys think???

I did this repair without pulling the lower manifold, as the internet videos I watched showed it to go just fine that way...

Ideas for what I need to do to straighten this out.

Appreciate some corrective suggestions for next steps for me to resolve.

Right now, thinking I have to just go back in verify FI cylinder correct routing, and put it back together again.

Thinking this I will add some RTV to the upper manifold base gasket.

Maybe its a base air/vacuum leak?

Thoughts?

Frustrated in Minnesota...

Thanks
Lfryklu

2 Answers

71,335

Well, these Vortecs are known for all this you are going threw. So basically I would start from scratch diagnostics on the fuel system, to see what is going on now. First have a new fuel filter on hand. Before putting it in dead head check fuel pressure (line only into gauge). Pressure should be 66 lbs min. & hold no less than 5 lbs. drop. With this verified, put in new fuel filter. Then check fuel pressure at the Schrader valve, it should be 56 to 63 lbs. Once it builds up pressure turn the key off, pressure should not drop more than 5 lbs. and hold for 3 min. If dropping more than 5 lbs. you still have a leak in either injectors, spider lines, or regulator. Now it is my understanding to replace with oem, and all of it. I think it comes as a hole unit. Regulators are what leak the most, but never heard of it lasting over 6 months before having trouble again. Another thing is that intake manifold is notorious for air leaking at the mating surface of the heads. Check the bolts and snug up. Do not over tighten. They only recommend like 11 ft.lbs. but I put mine at 20 ft.lbs. Check for air leaks with a can of carburetor cleaner along the intake and anywhere vacuum. This causes the lean condition that throws that code.

71,335

And a random miss fire is usually condensation (water) in the fuel. Put some gas additive in with isyoprofel in it...like the red bottle of heat.

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