My car took a while to start and was having a rough idle. It also has a coolant leak, but I think that is a separate issue. I wouldn't hear the fuel pump prime. I replaced the fuel pump and the main relay and still had the same problem. If I waited 10-15 minutes it would start.
I took it to the mechanic because I am not too familiar with cars. They could not recreate the slow start and said the rocker arm Orings were bad and letting oil into the spark plugs. They also said the water pump had a little leak. The car in not worth much so I didn't want to put too much money into it. It started perfect for a few days until it wouldn't start at all. I checked the spark plugs and they were full of oil. I put in new rocker arm orings, valve cover gasket, spark plugs, tube seals, and the spark plug wiring but it still won't start. There is spark at the spark plugs. The fuel pump won't prime unless I manually jump it at the main relay. I tried running the pump with the jump and then starting the car but that didn't work. I don't know what to do next. Any help would be much appreciated

 

Sounds like a classic case of the old ECU pooping out, which is generally caused by a failed electrolytic capacitor(s).

The capacitors cost pennies each, if you are willing to learn to desolder the old one and solder in the new one, which honestly is pretty easy.

 

I looked into it but I couldn't see any of the capacitors that are leaking. I would be willing to buy an ECU if that is the problem. I can find a used one on ebay for $100 that have free returns. Is that a reasonable next step?

 

Unfortunately, not all bad capacitors show visible signs of failure. The only reliable way to know is to remove them from the board and test them with a good multimeter or capacitor tester.

If you can't do this^, then shop for the best deal on eBay. I assume you have a D15B7 engine with a P06 ECU, which is not among the most expensive ECUs. Note: There are different ECUs for manual versus auto transmissions.

 

Mine is a P06-A50 automatic transmission. Is there any other ones that are compatible or do I just have to get the exact part number?

 

Exact, no. An eBay ad should mention if the P06 ECU is for an auto or manual. If it doesn't, look at other ads that do. eBay buyers have all the power, but be a smart shopper.

 

Honestly there are so few to replace you should seriously just replace the caps, I'm almost certain that is your problem. Tip. It's easier to gently pull the electrolytic cap body (metal cans) off their leads leaving the leads in tact so you do NOT have to actually solder the new leads into the PC board, just solder the leads on the new caps onto the old leads make sure they are not too long so the caps fit back in the ECU case. Post back with an update. EQUALLY IMPORTANT
THEY ARE INSTALLED WITH positive and negative polarity observed so you will see a "-" negative sign pointing to the lead which is negative and the positive will usually unmarked Remember when you remove the can of each original electrolytic cap to mark which lead is negative and which is positive on the board BEFORE removing the originals!

 

I ended up buying a new ECU and plugged it in and nothing changed.

 

clogged fuel filter- replace if you haven’t

bad rings- compression test wet and dry and make sure it is in spec. You can rent one at your local parts store.

fuel pump- check fuel pump relay or replace it located under the hood.

check your valve lashes too they might need adjustments if they haven’t been done in awhile.

 

If it’s a manual 5speed, check the clutch switch stopper under your clutch pedal, if it’s auto disregard this.