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You are in the GMC Safari & Chevy Astro
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GMC Safari, Chevrolet Astro, Van
#1515 of 1973 Re: fuel pump problems [fixitrod]
Dec 05, 2006 (8:20 pm)
Replying to: electricdesign (Dec 04, 2006 6:48 am)
Thanks for the reply. This is a GMC SAfari V6 with 260000 1995 with Auto tranny. I have posted info on the Safari site and responses ran out as to what to try.
When the key is turned the van makes a sound of the engine trying to start . I can see the belts turning and this has been described to me as "starting" but the engine will not "catch and fire up". This appears to be cranking but not turning normally.
Yes the starter worked on two benches and I as well had it refurbished and replaced the solenoid.
I can do the fuel compression check. I thought the engine had to be running for that so I will get my hands on a test unit and check it.
The van has new distributer and rotor and I replaced the plugs and wires but will check the "spark". I replaced the ignition coil because the resistence was not to specification per Haynes.
I replaced the fuel filter yet have not dropped the tank to clean it out. I would hate to think how I got "trash" in my tank. The van has been vandalized previously and there have been some mischief going on in the neighborhood.
The engine was running very well prior to the "rough idle situation...we had driven the van to Disneyworld in May. Actually while I was working on the rough idle I applied some fuel system cleaner and the next day or two is when it stopped starting...hmm? Any suggestions?How do I check the valve timing?
OK, First things First, lets get the terminology straight so that we are all speaking the same language here. Your engine is "Turning over" when you turn the key to start, that means the engine crankshaft is rotating and all related parts are moving. You engine "Turns over" but does not "Start". OK, we got that? Now, when the engine turns over, does it seem to turn over at about normal speed? Meaning does it sound very sluggish when it turns over, or more like normal? Next, I'm assuming it turns over about normal, and for now we assume it has spark, so the next logical thing to check is "Fuel Pressure" NOT "Fuel Compression" as you said. You use a strange mix of words that complicates simple things. Please try to stick with me on the correct terminology. You check the fuel pressure with the ignition on and engine off, because the electric fuel pump in the gas tank starts when you turn on the key. Do you hear the electric fuel pump start to run when you turn on the key? It should run for a couple of seconds or more, then stop as it builds up pressure. Do you hear it? If you DO HEAR it, the proceed with the "Fuel Pressure Test". If you DO NOT HEAR the fuel pump, then do the fuel pressure Test" to verify that there is indeed NO fuel pressure, then check the fuel pump relay and check the electrical circuit, there may be a reset button for the fuel pump. Consult your manual for locations. Once you have the fuel pump running and have fuel pressure at the fuel rail pressure test port on the engine, check to see how MUCH fuel pressure you have, I would guess between 30 to 60 pounds, but check your manual to see what the specs say the prssure should be. If pressure is ok and within limits, then proceed with further diagnosis. If fuel pressure is low, you need to find out why. You said you already replaced the fuel filter, but did not mention if the fuel that came out was dirty or not. You should always carefuly pour the fuel from the old filter over a white paper towel and look for any dirt, and Please put out your ciggarett before you start doing this! No open flames or heat sources anywhere near where you are working, Safety First! If there is dirt or odd color liquid, then you may need to pull the fuel tank, best to do this with the tank almost empty. The electric fuel pump in the tank has a filter/strainer on it that can possibly get clogged. It may need to be cleaned or replaced. If you have a problem with vandals in your neighborhood, you might need to get a locking gas cap. Once you determine that the fuel system is good and you have good fuel pressure at the fuel rail pressure port we will go farther with this diagnosis.
Next things to check if no start after the fuel pressure is known to be good:
#1 Ignition - Is there Good Spark at all the Spark Plugs? Are all the spark plugs clean and dry? (you can't fire dirty or fouled spark plugs)
#2 Check to see if fuel is getting into the engine - Spray a little gasoline or starter fluid into the Throttle Body intake while cranking the engine to see if it tries to start that way. If it tries to start, and you know you have good fuel pressure in the fuel rail, then there is a fuel injector problem or throttle Body Problem. If still no start, continue further diagnosis.
#3 Check to be sure the engine has the proper cylinder compression pressure in each cylinder. All cylinders should be within 20% of each other, and not low overall, check your manual for compression specs, I would guess that anything below 140 pounds would be low.
Let us know what you find.
P.S. and Yes, Disney World is very nice this time of year, I went there the day after Thanksgiving, it was really nice that day. March is good too, May starts to get too hot for me.
#1516 of 1973 Re: fuel pump problems [electricdesign]
Dec 07, 2006 (9:26 am)
Thanks for the reply. I will do better to keep the terms correct.
The engine sounds normal as it and the related parts are trying to start. After so many attempts it gets sluggish so I've been charging the battery and this helps but it still won't start.
I got a fuel pressure test kit(Yes it is running when the key is turned) and will proceed to test the pump pressure, spark plug condition and try spraying into the throttle body while attempting to start it to see if this will happen.
#1518 of 1973 Re: fuel pump problems [electricdesign]
Dec 07, 2006 (10:59 am)
Checked fuel pressure with a test kit and Haynes says it should be 58-64PSI and it is within spec, 59-60psi. I spray some ignitor into the throttle body and attempt to start. If it does not start I will investigate the spark plugs and if they are fouled I will replace.
At one juncture with this when I was trying to crank the van I heard a pop and smoke came from the top of the engine. This hasn't happened since but I wonder what that may have indicated...something sparked somewhere?
If they are OK then I will move to the injection system. This particular system is not servicable(CMFI) so it has to be replaced and is inside the intake manifold. At least I am getting some positive results so far...
#1519 of 1973 Re: fuel pump problems [fixitrod]
Dec 07, 2006 (12:27 pm)
Ok, You have good fuel pressure at the fuel rail on the engine, that means you should have fuel spraying into the engine, UNLESS the injectors are plugged or if they are not firing. Pulling the spark plugs will tell you a lot. First, check for a good spark at each spark plug wire. Pull the plugs, examine each spark plug to see if they are clean, fouled, or wet. If the spark plugs are fouled replace them, if just wet clean and dry them by spraying starting fluid or Brake Kleen on them. Test them by putting them on the ends of the spark plug wires, ground the outside shell, and watching them to be sure that they spark good. Don't put them back in yet. Get a good cylinder compression gauge that screws into the spark plug hole and check the compression on each cylinder, when you do this, unplug the coil so the spark plugs won't spark, block the throttle open, connect the battery charger to the battery, and crank the engine with the cylinder compression tester in one of the spark plug holes. Write down the cylinder number and its compression in pounds. Let the battery charge between cylinders if you have to, to be sure you get good and equal readings. After you do all cylinder compression readings, mark those as "DRY READINGS". Look up the specs to see what the compression should be, They should all be within 20% of each other and not low, I would guess that anything below 140 is too low, but 150 might be to low, so check the specifications. If you have a cylinder that is too low, or all seem to low, then you will need to investigate the cylinders and valve train further. If you have low cylinders, then you need to do a "WET" cylinder compression test, do the same as before, except squirt about a tablespoon of motor oil into each cylinder with a pump type oil squirt can right before the test. Write the results down and mark them "WET TEST". If the cylinder pressures rise significantly (20%) up to specs, then that would indicate a piston ring problem. If they increase only a small amount (5%), then the problem is in the upper cylinder area, it could be head gasket leak, or valve leak, head crack or leak, or valve train problem. After the compression test, remember to unblock the throttle and to plug the ignition coil back in.
If the cylinder compressions all checked out OK, then the next thing to check is to see if the injectors are injecting fuel into the engine. If this is the problem, the engine would start and run for a few seconds when you spray gas or starting fluid into the throttle body while cranking the engine. IF the engine starts when spraying the gas into the throttle body, then the next step is to determine why the gas is not going through the injectors. They are either be plugged or they are not firing. If this is the case, get a "NOID LIGHT" at the auto parts house and connect it to one of the fuel injector wire plugs. Be sure to get the right Noid lights, as they sell different ones for different cars. The light should flash when the injector is supposed to fire. If no flash, that means the signal for the injector is not coming from the computer. If the Noid light did not light, then try the Noid light on each injector wire, and see if it lights on any of them. If the noid light DOES FLASH, on every injector, then the injectors will have to be removed and either replaced or cleaned. You should use NEW O-RINGS when replacing the injectors, unless you are sure that they are very good.
So check all of that, and then report your findings back here, and we can diagnose further.
#1520 of 1973 Re: fuel pump problems [electricdesign]
Dec 07, 2006 (6:14 pm)
Thank you very much. I had a few questions to clear up my understanding of these methods
1. It appears that the plugs should be tested for "spark good" regardless if I clean wet ones or replace. This should give me also an indication of the condition of the wires carrying the spark?
2. Does "blocking the throttle open" refer to not letting the air intale valve close after opening it with the gas pedal or by hand?
3. Would "the battery charger" refer to a standard unit such as I use when I take the battery out for charging and hook it uo to an electrical outlet.
4. When you state "spray gas or starting fluid into the TB while cranking" does this mean while my assitant is turning the key I spray into the chamber. I did this nad got quite a minor explosion out the chamber and the van did not start. Thank God for relexes. A few hairs on the back of my hand ashed...the instructions on the starter fluid I picked up say to "spray for 3seconds and then start"? Which would be more effective. I'll move my hand next timebefore I say "hit it"
#1521 of 1973 Re: fuel pump problems [fixitrod]
Dec 07, 2006 (9:04 pm)
1. Yes, you want to be sure that you have good spark through the wires and you also want to be sure that the spark plugs that you clean are sparking good. You should not need to test the new plugs.
2. "Blocking the throttle open" means holding the throttle open while cranking the engine during the cylinder compression testing, this ensures that you get enough air into the cylinders to build up the required pressure. I usually work alone without an assistant, so I lodge a screwdriver of wrench in the throttle linkage to hold it open, and I use a remote starter switch to operate the starter, that way I can crank the engine while I am looking at the compression gauge. But if you are using an assistant, the assistant can hold down the gas pedal while he cranks the engine, or "hits it" as you say. Be sure the ignition coil is unplugged or disabled when compression testing so that they are not sparking all over the place.
3. A regular plug-in 12 volt car battery charger is fine, usually a 10 or 12 Amp one is enough. If the battery "tires", just give it some time to charge between cylinder tests.
4. It sounds like you have some backfiring going on. This sounds like it could be a timing issue, possible ignition timing problem or a valve train timing problem. The ignition timing should be good in modern cars, as it is controlled by the computer and distributor, unless something has been messed with to affect it. The other reason for backfire is the valve train out of time, caused by a jumped valve train timing chain or gears. If valve train is out of time, the cylinder compression will be low, that is one of the main reasons I wanted you to check the cylinder compression. Your vehicle could likely have a timing chain that has jumped, as your milage is very high on this vehicle, I think you said over 200,000 miles?
The starting fluid is very volitile (flammable), I would spray some in the Throttle Body, then move away from it, then have the assistant crank the engine. You might be better to spray a little gasoline in the TB, then back away, the gasoline does not evaporate as fast as the starting fluid. Just don't use too much, because you don't want to get the spark plugs wet. The advantage with the starting fluid is that it won't wet the spark plugs. Remember, Safety First, move your hand and yourself out of harms way before trying to start the engine.
I'm trying to remember your previous posts, I think you said your engine has a disributor. You may need to double check the timing of the disributor, be sure that the Rotor points to the Number 1 cylinder when the #1 cylinder is at the top of it's compression stroke, AND be sure the spark plug wires are in the correct firing order and that the spark plug wires go to the correct spark plugs. If the distributor timing is off or the spark plug wires are off, it would make your engine act the way it does. AND the distributor timing must also be correct so that the computer knows when to fire the fuel injectors, as the fuel injector timing ALSO has to be correct. I do not have any specific information on your vehicle or any manual for it, I can only give you general information. If you need to get into specific issues such as ignition timing, distribution or fuel injection timing or valve train timing, you will need to consult a repair manual or get an alldatadiy.com subscription for your vehicle, it has all the info you need.
Let us know how it goes.
Electric Designer In Sunny Florida
#1522 of 1973 Re: fuel pump problems [electricdesign]
Dec 08, 2006 (8:48 pm)
What occurances could messsed with the ignition timing?
How can I verify that the rotor points to the No. 1 cylinder when the #1 cylinder is at the top of its compression stroke?
After I changed the distributor cap and rotor there were two connetions which I had to rearrange.There is a diagram of the wire locations to the distributor in the Haynes manual which I followed to connect them. The van already had the problem with rough idle when this occured. I changed the spark plugs months. The van was running smooth until the rough idle that began this whole saga. It should have been showing some skipping long before now if the wires had been crossed up back then it seems? I'll be looking at the spark plugs and compression this Sunday and will get back with you
#1523 of 1973 Re: fuel pump problems [fixitrod]
Dec 09, 2006 (7:40 am)
I am trying to go over all the logical possibilites with you, check things in a logical order, doing the easiest things to check first. You allready determined that the fuel pressure is good, but I would not dive into those fuel injectors embedded in the intake manifold until a last resort. I don't have a manual on your vehicle, so the exact details of how to check the distributor setup and ignition timing should be in your Haynes Manual. The manual should show you a picture of the top of the distributor cap and identify which "tower" (wire connection post) is suppose to be for the #1 Clylinder. You need to be sure that when the engine #1 cylinder is at the top of it's compression stroke (ready to fire), that the distributor rotor is pointed at the #1 tower on the distributor cap. The best way to do that is with an assistant, remove the #1 spark plug, hold you finger over the spark plug hole, stay CLEAR of the fan and BELTS, and have the assistant "BUMP" the starter a little at a time until you start to feel compression at the #1 cylinder spark plug hole. Then remove the key from the ignition, put a long screwdriver into the spark plug hole intil it rests on top of the piston, then have the assistant slowly manually turn the engine with a large socket and extention bar on the nut on the front of the crankshaft. Hold and watch the screwdriver unitl it raises all the way up, the #1 cylinder is then at top dead center of the firing stroke. Back it up slightly to where it is about 1/4 inch before Top Dead Center, and you will be very close to the ignition fire point (close enough for this test), then pull the distributor cap off and mark where the rotor is pointing, put the cap back on, and the #1 wire tower should line up with your mark, or be VERY close. If not, you will have to investigate why. Besure to check that the #1 tower has the #1 spark plug wire attached to it, and that it goes to the #1 spark plug, Double Check to be sure that all the spark plug wires are in the correct firing order all the way around the distributor cap and go to the correct plugs.
I wonder what two connections you had to rearrange and why?
I havent had a car with a distributor in a long time, those coil packs are nice! The only thing better is the cars with the COIL ON PLUG (COP) ignition system, like my daughters 2002 Altima has on it, really nice, no high voltage spark plug wires!
Ok, check the rest of it and let us know what you find.
#1524 of 1973 Re: fuel pump problems [electricdesign]
Dec 09, 2006 (4:29 pm)
I really appreciate your responses. The Haynes book shows a good picture of the distributor cap and firing order. As I remember it was nos. 1 and 3 which were crossed up. I am certain however that this happened when the new distributor and rotor were installed on after the startin problem was already present. At most I tried to start it a few times with the wires crossed.
I am curious as to the "remote starter " you use to help you turn the cranshaft. Is this the type that is part of the remote start kits that can be purchased through audio shops or is this aspecial mechanics hook up to the starter circuit?