1998 olds has starting problem. starts and runs well most times ,but once in a while wont start. has spark has fuel auto xray code scanner showa no codes. check engine light does not come on .??? what do you think it could be?

Dont change things til u no cause. Fuel pump probly bad..car is old. Put key to on position and off three times..then try starting. If it gos then pump is stil good and thers a pressure leak in rail. But again its du as a maintenanc item

could be low compresion

The standard drill is : spark, fuel, timing. Pull a plug wire to test for spark. Give a shot of ether to see if it runs on that.
Cars nowadays don't have much timing anymore, some don't even have distributors. A computer runs it all.
To check the computer, you need a code checker.

vacuum lines

Could be a relay or other electrical issue.
You say it has fuel pressure and spark, if that were true it should run.
So it either does not have enough spark to fire the plugs under compression, or not enough fuel pressure going thru the injectors, or not at the right time.
You might want to check for trouble codes in the computer.
There has to be something missing from the equation when it won't start. You may have to check all of the plugs for fire and try some carb cleaner sprayed into the intake to boost fuel supply to find the issue.

If it does not use a distributor, the timing is not adjustable.
If you have fuel for the injectors and spark at the plugs, you would need compression and it should start.
Could be the spark plugs, or too much fuel, or too little, or other problems.
Once you know you have fuel and spark, you may need to use a scanner to check the rest of the components.

Hi,

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This is how your problem is solved in my shop. Out of the box, I'd say that you have a problem with the fuel management system. However, there's a good chance that it's something simple and inexpensive like a clogged fuel filter or water in the fuel tank.

My second area of concern would be the manifold pressure sensor which is loctated under the hood, center, rear engine area, above valve cover, mounted in bracket. However, you must remember that these nothing more than starting points and not guaranteed solutions.

First a little background for your edification. You may be aware of all this but we've never done business before and all assumptions are off the table.

For an engine - make that any engine and irrespective of manufacturer - to run, you need three things to happen inside the engine, compression, fuel and ignition, without any one of these components the engine will not run.

• Compression - Engine compression caused by crankshaft rotation and pistons moving up and down inside the engine block. If the timing belt or timing chain fails it will cause the camshaft to become out of correlation with the crankshaft or allow the camshaft to stop rotating. Either of these conditions will cause the engine to lose compression and sometimes cause internal engine damage.
• Fuel Delivery System - The fuel system includes: fuel pump, fuel injectors, pressure regulator, fuel filter and pressure lines. This system is used to supply fuel under pressure to the fuel injection system, the lack of fuel pressure or volume will cause the fuel delivery system to fail and the engine to stall or not start.
• Ignition Spark Delivery System - The ignition system components include: spark plugs, spark plug wires, distributor (if applicable), crankshaft angle sensor, camshaft angle sensor, ignition coil, ignition module, knock sensor and PCM (powertrain control module). The engine relies on the ignition spark to be delivered to the combustion camber at the correct time. If the ignition spark stops or is delivered at the wrong time the engine will not run or run poorly.

Whenever your engine cranks but does not start, runs rough, staggers, sags or cuts off, follow this Troubleshooting Guide. Some of these steps require a code scanner. They are costly but AutoZone will loan you one for FREE.

Most vehicles operate by the same principle; basic troubleshooting procedures apply to most cars.

• Step 1: Anytime you have a problem with electronically controlled components such as an engine, transmission, ABS brake, or SRS (supplemental restraint system, Air Bag) inspect all fuses using a test light and check the under hood power distribution center and under dash fuse panels. If all fuses test okay continue to the next step.
• Step 2: To check for problems with electronically controlled components such as an engine, transmission, ABS brake, or SRS (supplemental restraint system, Air Bag) and the fuses test okay a trouble code scan is needed to identify any system trouble. Use a simple scanner tool to retrieve trouble codes and see if they relate to the specific problem, like a crank angle sensor failure code. If the trouble code present does not pertain to the immediate problem like an EVAP code ignore it until a later time, after the car is running.

The reason we repair non-related codes after the engine is running is because sometime false codes can be triggered by the engine not running. Once the engine is running again the code present might cycle and turn itself off. You might say "if the engine doesn't run shouldn't it have a trouble code?" Sometimes conditions occur that will not be detected by the computer, example: if the fuel pump fails the computer cannot detect the failure, so the engine doesn't start and the computer thinks everything is okay with no codes. If no trouble codes are present proceed to the next step.

If you have trouble using the code scanner or interpreting the codes click on the following link and use my access code (carrepair): Free Automotive Repair information for Users of a Code Scanner www.repairpath.com

All the best

Ben

Need t check the basics first....are all fuses OK?
Needs spark at the spark plugs
Needs fuel at the plugs
Needs good "suction"
Once checked one of these will be absent.

Things that you need for the engine to run
1- Fue
2-Air
3-Spark
4-Timing
5-Compression
your error codes will help you determine which to address

either have a shop scan it for trouble codes or buy a scanner your self at local parts store have OBDII scanner and find out for your self it could be a number of things.