Interesting Fuel Pressure Readings
 

Been working on a 2000 Blazer that will be my kid's car when he turns 16. Bought it in October so I could work on getting it up to snuff over the winter. Runs like a top when warmed up, but found out it has starting issues below 10F. No codes. Was almost like something was shut off when it was that cold. I couldn't smell any fuel, or get it to fire up even with starting fluid down the throttle body and my charger starter on the battery.

So I started by renting a fuel pressure gauge, tested while in my heated garage (I have it up on stands doing a few things right now). Getting a solid 61psi at the test port, then after shutting off pump drops to 55, then slowly goes back up to about 60! Holds there for over 10 minutes no problem. Thought it was the rented gauge, but yesterday I bought my own (Harbor Freight cheapy), and got the same readings. Haven't done a direct check off the filter yet, been having a hard time finding the parts locally to make an adapter hose. Hopefully I'll get the right ones tonight. Hoping the fuel pump is fine.

Anyway, I know nothing has been done to the motor, other than someone replaced the spark plugs and 1 spark plug wire, and cleaned out the top of the throttle body. I am planning on just going ahead and ordering the MPI spider upgrade, and doing upper and lower intake manifold gaskets with the new FelPro ones. Also going to replace dist cap, rotor, and new spark plug/coil wires so they all match. The one wire that was replaced is 5K Ohms difference between the factory wires....

Is there something else I should be looking at replacing to help with the cold start issue?

Replace the fuel filter with an ACDElco, They are like $10 -$15. Don't buy a cheap one, you will regret it.

For sure. Already done :icon_beerchug: Good call though.

The ignition control module (on the same bracket as the coil) can cause cold start problems.

Thanks Rusty, I did look into that and the coil as well. When it was -12 the one morning I heated it up really well with a hairdryer and it didn't help. I never did check spark or fuel pressure while it was that cold because, well, it was cold and I didn't want to deal with it. After getting it into the garage, fuel pressure is great and spark was fine as well. After getting the plenum off last night and seeing the poppits, pretty sure they were getting clogged and when it's that cold not getting enough pressure. May have a leak from the injector as well, but doesn't really matter, it's getting replaced. If it still is a cold start issue after the new injector, gaskets, spark plug wires, etc, I'll just go ahead and replace the ignition module then go from there. (probably to the crank sensor)

You serious? How (or what) did you measure...? Cause it doesn't look real to me.

I wonder if it's possible to extract the spider out, hook up to the fuel supply/return line, crank the engine and see if the poppets blow the fuel out. That might be faster and cheaper....

Mike, I measured the resistance of the one spark plug wire that was not original. 6K Ohms vs about 1.3K on the originals. Nothing to do with fuel there. I don't really care about the spider, I have a new MPI on the way, and the top end is tore apart since I'm doing gaskets anyway.