98 Blazer starting problems

--- Fuel System Problems ----

Fuel pump - Test, connect up gauge and watch it when you turn on the key, Gauge HAS to hit 55psi minimum, higher (up to 65 psi is better). Now start the engine, fuel pressure should stay the same, SNAP the throttle, Pressure should show a momentary change due the the change in vacuum.

It may not be the PUMP itself. BUT the check valve that stops the fuel from draining back is part of the pump, it's on the outlet side of the pump and is designed to A - hold pressure in the system so the vehicle starts when hot (the pressure in the system helps prevent vapor lock in the injection system) B - works with the regulator in the engine to control fuel pressure.

Common symptoms of failure - long crank times, poor starting.

It could be the pressure regulator, that is inside the intake on the injector unit itself. It maintains fuel pressure (55psi MIN. required for the system to operate properly) in the system and uses vacuum inside the intake to control the pressure and volume to the CPI unit based on engine load.

Common symptoms of failure - long crank times, poor starting, lower fuel mileage, smell of gas from the intake.

It could be a problem with the "fuel nut assembly" (AKA the fuel lines just inside the intake on the left side of the engine) they are known for cracking from heat/vibration.

Common symptoms of failure - long crank times, poor starting, lower fuel mileage, smell of gas from the intake.

All of the above are KNOWN issues with the fuel system on the 4.3 All can be tested with 2 pairs of vice grips and a fuel pressure gauge.

Connect gauge, turn key on, watch gauge. Fuel pressure should jump up almost instantly to 55-65 psi and stay there. (This is because the initial key on triggers the ECM to turn the fuel pump on for 3 - 4 seconds. This is to prime the rail because minor leakage in the system components is normal and the pressure may only be 30-40 psi. after setting overnight.)

If the gauge jumps up fast and stays there with LESS than a 10psi drop over 5 minutes the above parts are OK and the problem is elsewhere.

More likely is the pressure will drop very fast, that signals a leak in the system.

So you take the vice grips and go under the vehicle. (The next steps depend on which fuel lines you have, The earlier trucks had metal tanks and rubber flex lines, later trucks have plastic flex lines and the last ones have plastic tanks and plastic flex lines)

There will be three lines, One is pressurized fuel to the engine, one is fuel return to the tank and the last is a vacuum line (works with the EVAP system).

Look them over for ANY leakage. (especially right at the kick-up in the frame right in front of the rear wheel on the drivers side. The fuel lines and rear brake line are there and it collects a LOT of crap and rots the lines.)

You need the pressurized line first. Have a helper turn the key on, as soon as the pressure builds clamp off the pressure line. Watch the gauge. IF the gauge stays where it was when you clamped the line,(with no more than a 10psi drop in 5 minutes) the leak is the valve in the pump. (Usually requires pump module replacement as nobody makes a replacement valve, the original is molded in the top of the module. Sometimes it is rust/dirt blocking it open and you can clean it.)

Still leaking down - Release clamp, turn key on again, when pressure builds clamp off both the pressure and return lines. Watch the gauge.

Pressure holds with NO drop - Pressure regulator is failing internally and leaking fuel back to the tank. Replace pressure regulator. (inside the intake manifold)

Pressure still drops (even a small amount of drop is bad)- Either the pressure regulator, spider unit or the lines are leaking inside the intake. All require the intake to be opened to replace the parts. IF you are going in there plan to replace the FPR and the lines at a minimum. They may be OK now but they WILL fail. The new replacements are better parts.

- Has very good prices and top notch parts.

I usually opt for the upgrade to the "mini-injector" unit from the stock CPI unit, it's a direct bolt in (in most cases, call them and they will make sure) and greatly improves the system.

The above is based on multiple repairs to these systems by myself, and a LOT of discussions with other techs and mechanics about this system and improvements that are possible. (It applies to ALL of the CPI equipped GM engines both V6 and V8)

Yep, always amazed at people who think 45-50 psi is good on these.

After an hour of begging, I got permission to tell you that's not true.

. Christopher A. Young Learn about Jesus

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Thank you. I'll save this post, in case it's needed. For now, the truck is doing reasonably well.

Jan 15, 2014

Chevrolet Tradesman, with 350 engine (I think it's a 350). Been giving me starting trouble, for last year or so. More so when it's wet.

Latest "hurrah" was when I changed the distributor cap and rotor, and started nicely after that. Whew, got that one finally.

Today, needed the van for a service call. It almost started, but not quite. Tried the starter several times.

Took the other car to the call, and managed to git r dun.

Came back and tried a bunch of things. What seemed to help was to spray the fuel injector sprayers with some trichlor degreaser. I couldn't find my toluene carb cleaner spray.

Starts a lot better, now. Hope that does it. Thanks to all here, who offered ideas.

Could be the fuel pump is intermittent. Our 95 gave the granddaughter a bit of trouble. She wisely drove straight home where fuel pump dies in the drive way. We were able to get it going again but not for long. New pump all ok.

May 19, 2015 Just for grins and giggles, decided to look through my reciepts and see when I replaced the spark plug wires. Could not find any such reciept. Went to the store and bought a set of wires, plans to install them tomorrow when it's daylight and a bit warmer. Could have sworn I changed the spark wires last night.

Plans tomorrow to run the engine and water down the spark wires, see if that kills the motor. This hit and miss bit of throwing parts at it nonsense is no good.

- . Christopher A. Young learn more about Jesus .

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Need the van for a service call. Skip the wet wires step. Change the wires. The two front on driver side were nearly impossible to reach, so I left em. Six out of eight is better than zero out of eight. See when it rains, next.

- . Christopher A. Young learn more about Jesus .

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Your luck it will be the 2 you didn't change crossfiring causing your hard start.. Next sunny day when you have a bit of spare time, change them. I'd capitalize that but I don't want to hurt your sensitive little ears. If you don't have any spare time, make some.

Heard you about luck. The reason I didn't change cylinders 1 and 3, is that there is nearly no room to work. Under the brake cylinder, steering wheel, and a bracket of some kind. There is a chance I could have reached in, but the other six were miserable. It's not a question of time. It's a question of being able to reach them, and not wanting to cut my hands.

- . Christopher A. Young learn more about Jesus .

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It's your truck. Do as you like, but don't bother asking why it doesn't start or misfires next time. Take the time to replace them yourself or pay someone who can. I've replaced many of them. Not simple, but definitely not rocket science. Do it with the engine cold, of course.

If I had a choice of capital words, or bossy and commanding, I'd take capital letters.

- . Christopher A. Young learn more about Jesus .

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Monday June 01, 2015

Well, you might just get the last laugh.

Rained on Saturday and Sunday. Today I tried to start the van, it behaved totally the same as before the six wire service.

I dragged out a battery booster 50 amp, which did start the vehicle after about five tries. Each try, wait 60 seconds (by wrist watch) to let it charge. Makes me wonder if I have a weak battery, or slow starter?

- . Christopher A. Young learn more about Jesus .

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I'd put money on a slow owner, myself!!

That really adds intelligence to the conversation.

- . Christopher A. Young learn more about Jesus .

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If the bad wires are crossfiring it makes the engine turn over a LOT harder than if the wires are good and firing where they are supposed to. Did you do a voltage test when cranking? How about a starter current draw test?. Not hard to tell if you have a battery problem, or a starter problem.

Sunday June 28, 2015

I could check voltage, but don't have the DC ammeter.

Saturday I drove the Blazer, to a service call, and it rained all day. Sunday the Blazer won't start, but the van will. Took the van to church, home, dinner, and an emergency service call.

Supposed to be warmer and drier tomorrow, hope the Blazer dries out enough to start.

- . Christopher A. Young learn more about Jesus .

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Rained, Saturday. Blazer runs fine. Sunday, cool and humid. Blazer won't start. Monday, taking the time to see if I can fix the Blazer.

Distributer cap and rotor. No joy. Remove all four multi pin plugs off computer, spray with WD-40. Ignition module (next to coil). No joy. Replace ignition coil. No joy. Replace crank case position sensor. No joy.

No spark at center coil wire (using my old tester from when I did lawn mower repair).

What else might be wrong? Distributer pickup coil? Some thing else?

On Mon, 29 Jun 2015 20:35:52 -0400, Stormin Mormon wrote:

First things first - is there power to the positive side of the coil??? If not, find out why.

If you have power to the coil, the only other possibilities are module or pickup coil (or both, A bad pickup coil can cause the module to fail prematurely.), the crankshaft sensor, or wiring. Failure of the crankshaft position sensor is a very common problem on the Blazer 4.3L engine and so I would troubleshoot that first. It has a 3-wire connector, a green 12 volt power wire, a gray ground wire (center wire), and a beige signal wire (the wire closest to the mounting bracket bolt) which sends a 5 volt pulse signal to the PCM to activate ignition spark. You must leave it connected to test it for a pulse signal. Use a multimeter set to DC volts and pierce the beige signal wire (the wire closest to the mounting bracket bolt) with the multimeter red lead and touch the multimeter black lead to a good ground and then either have someone crank the engine or turn the engine by hand with the ignition switch in the ON position. If the crankshaft sensor is working the beige signal wire should produce an on/off 5 volt pulse> If there is no 5 volt pulse you should unplug the crankshaft position sensor connector and with the ignition switch turned to the ON position and the multimeter set to DC volts, probe the green wire connection on the plug with the multimeter red lead and touch the multimeter black lead to a good ground to see if the crankshaft position sensor is getting 12 volt power and then switch the multimeter to ohms and do the same at the gray wire connection on the plug to see if the crankshaft sensor is getting a good ground. If it is getting 12 volt power from the green wire and it is getting a good ground from the gray wire but it is not producing an on/off 5 volt pulse then it is defective. If the crankshaft sensor fails intermittently the check engine light will come on and the engine will continue to run but if it fails completely the engine will quit running and will not restart and sudden complete failure of the crankshaft position sensor is common on that Blazer 4.3L engine.

My suspicion is you don't have 12 volts at either the coil or the crank sensor.

If you have 12 volts at the coil AND get a pulse from the crank sensor, the module or module wiring is suspect.