jwatheyjr

I have a 1989 Prelude and am having a problem, maybe with my fuel pump. A couple days ago, I went to start me car and it wouldn’t start – I noticed that when I turned the key, the fuel pump didn’t go (just a habit that I always pause and listen to the fuel pump before I turn the key). This morning before leaving for work I tried it again and the fuel pump came on and the car started. I did this a few more times and the fuel pump came on probably 60% of the tries - and whenever it came on the car started.

QUESTION: Is the problem likely in my fuel pump, or could it be something else (short, or other) that could be restricting electricity to the fuel pump? Since it is working sporadically, should I assume that it is okay and look elsewhere for the problem?

Any help or advice would be greatly appreciated.

James

syntax.

main relay failure is a common problem that would cause symptoms you are describing. does it happen more after its been sitting in the hot sun?

jwatheyjr

Possibly - I hadn't thought about that. Yesterday afternoon I tried starting it and the fuel pump didn't kick on at all after quite a few tries. And then early this morning it worked sporadically.

Duane_in_Japan

These are some of my posts, they are mixed up but will get them straight some day.

Use two long but thin common screwdrivers to pry the two outer sides (top & bottom in this view, put drivers next to the two tabs, not on them) of the relay cover out away from the relay inner portion and gently pull down on the wire harness to gain access to the internal section PCB for closer inspection and usually easier replacement of the unit, I do not replace the outer housing, it is always very easy to just pop it out of its shell and replace it as a sub-unit instead of unbolting the shell mount from its mount point which may be in a very difficult location to access.

You are correct, there are two relays in the main engine relay unit. The FP half only controls the FP.

If you have some further in depth electronics understanding it takes more amps to pull the switch closed than it does to hold it closed. If you are loosing your control switch then just replace the main relay. Isn't it around 50 bones, it is a high wear and tear item and the other half will go out in short order. If it is dying while the pump is running then it is bad from its own generated heat and loosing its own magnatism ability. If the main ECM is not controlling the ground then I completely understand why you want to give it a permanent ground.

If the relay is weak then just stuff a 16G jumper wire at the two switch terminals #5 & #7 to test if the relay is bad and the fuel pump is good.


I am assuming that you are going to swap it for several days if needed to get both cars good and hot on the inside. Some techs turn the heat on while sitting out in the sun to see if the car will die but does not always work. Remember to keep both cars parked out in the sun. Others will heat up the relay with a blow drier.

Checking the plugs for fuel is the long way, on top of your fuel filter or in the fuel injector rail is a small 12mm nut (fuel pressure gage test port plug). Crack it open, a little residual fuel may drain out so keep some rags under the filter. Turn the key till the idiot lights come on (KOEO / Run) and the computer will fire up the fuel pump for about three seconds via the main relay. No squirting of fuel = possible bad main relay. Tighten the 12mm nut, lay down under the steering column, turn the key to try to start (cranking mode) and smack the main relay with screwdriver handle, car may start = bad main relay. Keep the door closed while trying these couple of tests, all the hot air will escape quickly and the main relay may start to work on its own.

Get in car, close door and window, no start, check fuel squirting, tighten fuel test port plug, get under dash, crank car, hit relay and see if car starts = bad main relay.

Honda is a speed density system, it uses a MAP sensor instead of a MAF sensor so you can pull the intake hose off coming from the air filter. Spray the throttle body with a bunch of good brand carb cleaner and the engine should start for a few seconds, now you know that timing, ignition and mechanical problems should all be ok. Get on to testing the main relay and fuel pump (test at the main relay).

jwatheyjr

Thanks for the advice. I have ordered the parts, so hopefully I will be able to report back next week with good news.

I was recently in Tachikawa (working near Fussa) - the Tokyo area is huge!

James