Hello and thanks for any help you can offer.I have a 1995 Blazer that I have owned for many years.Last winter I had issues where it would start but run really bad as the outside temp dropped, The colder it got the worse it would run.I decided to let it sit till spring and once the weather warmed I was able to drive it again .Here we are with cold weather again and it's doing the same thing just as I figured it would.It was 35 here the other day and it started and ran ok...and ran better once it is fully warmed up.Today it was below zero and it would start but died right away, it will continue to start and die but after a bit it will continue to idle but will pop and backfire through the intake..also has a very very bad hesitation.. This blazer is just something I use to run around in but I do want to get it running right.
This Blazer is the model that in 1995 they went to the obd2 system mid year ..my blazer has the obd2 connector with the obd1 system...I have found no one who can scan the codes in it and I tried the paper clip method but it would not flash anything.I am trying to avoid the dealer because it just isn't worth that much money and I am on a budget.I understand that throwing parts at it is costly as well but so I am hoping these symptoms might ring true to someone who has had the same issues.
What I have done so far
Plugs and wires...did not replace cap and rotor
air intake sensor
coolant temp sensor
The fuel pump failed last year and I installed a new tank and pump assembly in it...fuel pressure is within listed specs and holds pressure after shutting it off
tested tpi it tested ok
tested map it tested fine
I am wondering if crankshaft sensor could cause cold weather issues?
Could a cap/rotor be affected by cold?I know damp weather can be an issue.
Any help would be greatly appreciated.

 

On late 95, yes, the cap & rotor are very important, they need to be AC Delco.
Not likely the crank sensor would be temperature related.
Rule of thumb is: If a sensor is out of range, it will set a DTC in memory and turn the check engine light on. No light, no problem. Holds true 99% of the time. There's always an exception to the rule..... The exception in your case, could be if the IAT or ECT sensors are within range, but not accurate, it will cause a problem cold, and NOT turn the light on. You'll need to access the OBD1.5 system to check their accuracy.
Low fuel pressure or volume will cause a hesitation, guaranteed. You'll need to test pressure and leakdown at the service port and at the fuel filter outlet to tell if your fuel delivery system is working properly. Testing your 1995 CMFI is the same as 1996 & newer CSFI, but the specs are different. This link explains how to test it: https://blazerforum.com/forum/2nd-ge...eakdown-88305/ There is a parts list at the end for building the necessary adapter.

 

Thanks for your reply..I decided to recheck fuel pressure again today..
key on eng off was 60 psi
less than 1 psi leak down after 10 mins/
running I am getting almost 90 psi!!! ??
I do trust the snap on gauge I am using would this be a regulator issue?

 

Were those reading both at the service port? When you say "running", do you mean the pump or the engine?

EDIT: Checking regulated pressure at the service port requires the fuel pump to be running, and the engine off. When you initially turn the ignition to the RUN position, the pump will activate for about 2-3 seconds and then shut off. Pressure must be checked while the pump is activated, (running).

 

yes both at the shrader valve behind plenum.I checked pressure with the key on but eng. off and it was 60 psi
I let it bleed off for over 10 mins and lost less than 3 psi

With eng running the pressure is 85 to 90 psi Gauge needle pulses a bit but that is the range.
I have pulled the plenum to look for issues on fuel reg and spider. what I have found is no gas in the lower intake, but there is some eng oil laying in different areas? Would this be normal/
I also checked fuel press with plenum off to look for fuel leaks at reg but see none.

I pulled a couple poppets out and see no oring on them? Normal?

Also a note... last spring when I changed the fuel pump I did my pressure tests and the results were the same as the ones posted above except with the eng running the pressure was within the normal range and not high like it is now..also the pressure reading was showing that after the key was turned off the pressure would bleed off somewhat faster than what is considered acceptable.The vehicle always started right up and ran fine even with the bleed off so I did not do anything with it.

Are the poppets replaceable on their own or would I need the entire spider assembly?

Thanks for the help!

 

Your key ON, engine OFF pressure of 60psi in post #5 may have been after the pump shut off. We need to know the pressure with the fuel pump running, and the engine off. There is definitely a problem with your fuel pressure, but it must be tested correctly.

Read the "EDIT" in post #4.

 

ok key on pump runs 3 secs and pressure shows 80 psi then drops to 60 psi
also found the ground wires on back right corner of block to me corroded and greasy ..cleaned them up.

 

Now we're gettin' some where

Regulated pressure is far too high. Only two things can cause that:
#1 Fuel pressure regulator set too high.
#2 Restriction in the fuel return line somewhere between the regulator and the tank.

The service port is in the 3/8" pressure line from the fuel pump. The return line is next to it at the rear of the manifold, and it is a 5/16" line. Disconnect the 5/16" line and stick a piece of rubber hose over the fitting that goes into the manifold. Direct the other end of the hose into a bucket. Check regulated pressure again, just like you did in post #7, and post the results.

 

Thanks again for responding..as I posted earlier I currently have the plenum off so checking pressure running is something I cannot do right now. However I did remove return line fitting and slipped a length of rubber hose over it..I was able to blow through it and could hear gurgling in the fuel tank so I am confident there is no blockage going back to the tank. Is there a way to check the regulator? I am thinking the reg could be the issue but have not read of excessive fuel pressure with eng running .

 

You can activate the pump with the plenum removed, just like you did in post #7. Pressure should be 55psi to 61psi with the pump running. Blowing through the lines doesn't tell us what regulated pressure is, and that's what we need to know. It's also not accurate, or healthy Instead of blowing in the hose, move it to the line coming out of the manifold, stick the other end in a bucket, and activate the pump. Work with me here and I'll tell you what the problem is