Cold Start on 1997 Blazer

[cybermoser]

I have a 1997 S-10 Blazer with a 4.3L (W), lately have have been having problems starting it when it is cold.

I performed some diagnostics last evening and here is what I came up with. Looking in the Chilton's manual for the 97 S-10 Blazer under Fuel Testing page 5-10, item 7. "Monitor the fuel pressure with the pump running. The pressure should be 60-66 psi (415-455 kPa)." I monitored the pressure and it never reached 60 psi. The highest reading I monitored was 50 psi. From this reading alone I think I should be able to say my problem is either a bad/faulty Fuel Pressure Regulator or a bad/faulty Electronic Fuel Pump in the gas tank. After seeing the 50 psi. reading I then let the pressure gauge attached and checked it after setting for 1 hour, the resulting reading was then 40 psi. I then left the engine set over night for 7 hours and when checking the reading then found the reading to be 0 psi. I am not sure what the timed readings should be. I replaced my fuel filter 5 days ago thinking that was the problem, so my filter should not be causing the under pressure readings. Can 10-16 psi. cause a cold starting problem? My next question is how do I narrow the problem down further? Is there a way to check to see if my Fuel Pressure Regulator is working properly or not?

With finding that the Fuel Pressure is only 50 psi., can I safely say that I do not have a problem with my poppets?

What sensors might be schewed? I am not getting a check engine light. It has been starting kinda hard for the last 3-4 months, I just thought it had water in the tank so I have been running Heat through it I also ran a bottle of GumOut Fuel Injector Cleaner through it this week, thinking it maybe dirty injectors. However just the last 2 weeks is where it has really been acting up. When I go to start it after it has been setting for a while the engine just cranks and cranks. I found that if I turn it over briefly then shut it off, wait 5-10 sec, then turn over again and repeat this procedure 5-10 times the engine then starts, and it kinda seems that the engine is then loaded up with fuel, not sure but the engine kinda studdars for the first 2-5 secs of running.


I have also found that by jumping the vehicle with another vehicle, giving the fuel pump more juice per say, the blazer will start a lot faster. I have found an article on the web at

http://www.netprofitgarage.com/displ...=npgefi803.htm

The following is an excerpt

GM CPI (Central Port Injection) and SCPI (Sequential Central Port
Injection)

Note: Acronyms and names for these two systems vary - they're also
known as CMFI for Central Multi-port Fuel Injection and CSFI for
Central Sequential Fuel Injection. Take our pick.

Given the success of the TBI concept, I suppose it isn't too
surprising that the smart engineers at GM found a neat way to wed
the concept of the low cost of one central fuel injector to the
benefit of a dry intake manifold. They did this by incorporating a TBI-
style injector with a "spider-web" of plastic tubes and poppet valves
that led through the intake manifold and down to the back of the
intake valves. Obviously, with only one fuel injector the system could
not be sequential; that is, the injectors could not be timed to fire at
a few degrees before intake valve opening, the optimal way to
introduce fuel in to a cylinder. Nevertheless, if you've ever driven a
Vortec-equipped Chevy S10 Blazer or pickup, you can appreciate how
well this system works.
Low-end torque is very good, much better than that of the same
4.3L motor equipped with the standard TBI unit.

From a service standpoint, however, this system has its weaknesses.
There are two problems that have ended up being pattern failures.
First, the system runs at higher fuel pressure than what we are
accustomed to seeing, 56-64 psi. The poppet injectors will not open
reliably with much less than 54 psi. I believe it was the Vortec cold
hard start problem that was the inspiration for the concept of
checking fuel pump rpm by means of the low current probe and the
lab scope. The problem occurs during cold mornings when battery
voltage is not what it might be. During cranking, voltage to the fuel
pump drops. The rpm and consequently the pressure of the pump
goes below the level necessary to open the poppet valves. Some of
these hard starters took months to diagnose because a tow truck
driver would hook up his jumper, and voltage would rise high enough
to gain the extra two or three pounds of fuel pressure. Or, the
vehicle would be towed in during the cold morning, but by the time
the shop got around to checking the vehicle, the ambient
temperature had warmed enough to kick up battery voltage, and the
thing would start. Techs who were in the habit of not looking stuff up
would see over 50 psi on their gauges, and, of course, that had to be
enough! Sharp guys like Jeff Bach (current probe guru) and Jim Linder
(the injector guru) learned how to scope the fuel pump waveform
with the lab scope and calculate pump condition and rpm, almost to
the point of being able to predict what day of the year the vehicle
would fail to start!

The second common problem with the CPI system was the gradual
failure of the fuel pressure regulator diaphragm. This could be a real
pain to diagnose, as it had virtually no impact of fuel pressure.
Rather, because the regulator is located inside the intake manifold, it
would leak fuel and cause a rich condition under circumstances that
seem to vary from vehicle to vehicle.

Sometimes, when the failure is large, the engine will blow black smoke
and perform very poorly. Other times, when the thing has just begun
to leak, it will cause a lumpy, erratic, hunting idle condition as the
computer tried to deal with the blobs of fuel coming from the leaky
regulator.

The best way to diagnose these is the good old visual inspection. If
the intake manifold runner control valve is removed, you can get a
good look down inside the intake. A mirror is required on the vans,
but it is generally possible to see the fuel washdown that occurs
when the regulator starts to leak. Formerly, it was necessary to
replace the entire spider-web assembly when the pressure regulator
leaked, available from aftermarket sources as well as from GM. But
Doug Garriott of LTS (Linder Technical Service -- Lindertech.com)
tells me that they have shipped over 500 of their custom-engineered
replacement fuel pressure regulators and have had very good
success with them.

With all this said, I still do now know if my problem is my fuel pump or if the problem is my Fuel Pressure Regulator. I need to know if there is a way to test the Fuel Pressure Regulator. The above article states a visual inspection by removing the intake manifold runner control valve, what is this valve and where is it located?

Please help!

[rlith]

To see if it's your injector unit, pull the upper plenum and look for signs of washing (where one side is cleaner than the other)... If the passenger side is leaking, it's the spider pod, if it's the driver's its the nut kit.. If they are both alright, then the most likely culprit is the fuel pump..(I lean towards the fuel pump since you say when you jump it it starts quicker)..

[vinnie97]

have u checked for a good ground connection for the fuel pump?

[Jeremy-WI]

Well if you wanted to cure it, you could replace three items, fuel pump, fuel pulse dampener, and fuel pressure regulator or if you had the diagnostic procedure from the service manual, you could narrow it down, but if it was the regulator you will still end up dropping the tank to check the pulse dampener for cracks or partial disconnect

[Bronco2]

Poppet? Whats a poppet? If you mean injector, the 4.3 W has 1 big one feeding all 6 cyls. These rarly give trouble,the rest of the system goes first. The intake runner valve is located under the plastic cover that says Vortec on the intake. Remove the cover,the valve is on top,2 torx screws to remove-this will let you look in the intake for fuel washing. However I think your problem is fuel pump related,because if any fuel was leaking in the plenum you would have a sever over rich condition.If you go to the Blazer/S10 forum section,you will get a lot of good info.

[Jeremy-WI]

A 97 would have 6 injectors, its a CSFI setup not the old TBI. Service manual states that fuel pressure under 60 will likely cause hard start issues and a fuel pressure of 40 at idle is undrivable

[97blazer1]

Hello, Thanks for taking the time to answear me (Hopefully). My 97 blazer 4.3L will die after running for awhile. Then I noticed when I try to start it there are no lights coming on on the dash. Then after about 10 - 20 secs of cranking lights come on in dash (idiot lights) then 2 secs more and vrooom starts running. Any Ideas. Thanks again.

[rlith]

97blazer1 Umm, yer hijacking this thread, start a new one

[luscombe8]

The reply I am posting is more serious than just sensors failure. My Blazer also had a starting problem that once the engine was running, it seemed to sure when driving hard up hills, sometimes stumbling under normal loads and gentle misfires under light conditions. It also would idle rough at times and then smooth out at others.

Following the normal diagnostic procedures, produced little because there were no codes being generated by the sensors.

An inspection by merely removing the manifold tuning control (on top of the plenum) and looking into the plenum where the spider could be seen resulted in fresh fumes rising when the key was turned on.

This told me that there was a leak.

GM has an engineering fault with this system by crossing fuel injector lines for 3 and 5 cylnders under the high pressure fuel line to the spider. This results in chaffing or barking of the plastic lines.

In my case the lines actually wore through causing a pin hole leak that would cause the fuel pressure to drop after sitting for a short period of time resulting in a very hard start necessitating the gas pedal being floored to get the engine to start, shooting black smoke out the tailpipe.

An explosion or fire will result if this condition is duplicated in other cars, and it will because of the design flaw. All one needs is an ignition source and the whole top of the engine will blow off and a fire will result.

This pressure fuel line must be replaced, a new spider must be installed and a piece of rubber may be inserted between the fuel lines to minimalize the wear.

Start with the inspection and perform the maintenance described or there may be very serious results from this flaw.

[tom3]

For the original post, the hard start here is no doubt the fuel pump. Might try turning key on and off several times and let the pump run its short cycles, build up fuel pressure some, then try to start. Often it will start right up at that point. Replace the pump. Easy to pull bed off truck and access the pump from there, and good way to clean up everything while the bed is off.

[BlazerLT]

He said that if he jump started the vehicle with anther truck, the truck would start much faster which leads me to believe that his battery is almost gone and not outputting what it should be.

I would check the battery first.

[blazer1099]

Just wanted to let you know I had the exact same problem as the original post. When we measured the fuel pressure it was about 52. But this was not enough to allow the engine to start when it was cold.
So, we put in a new fuel pump and this got the presure up to about 62. Now it runs great! Thanks for your help.