NeCr0mStR

iTrader: (3)

Ok so posted earlier a couple weeks ago I had a problem with hesitation and bucking at various rpms and under different loads. Well I got in the car today to drive it and it would crank but no start. I wasn't sure if it was flooded after a couple attempts, so I deflooded and tried again (because its a 91 I can use the gas pedal trick). Well tried a couple more times same results, checked to see if I could hear the hum of fuel pump but I can't tell. Pulled the rear leading and trailing plugs and they are just sooty with no fuel smell, or any kind of wet on them.

So what do you people think? Fuel pump most likely? And is a Walbro a good option as just a replacement or is that too much for what I have?

I have a 91 na, with a stage 2 street port from Atkins (I don't know how aggressive) and I have a RB true dual exhaust. Future plans are for an Rtek addition this winter, and perhaps larger injectors if needed.


Any advice much appreciated, I will prolly pull the tank this weekend unless someone has a better plan to test the fuel pump.


Thanks again

scrip7

iTrader: (6)

Have you tried to start the engine with carb spray to see if it will run at all?

There's no need to pull the tank to remove/ check the fuel pump as it is thoughtfully accessible by pulling back the rear carpet and removing the access cover. Start with a voltage check at the fuel pump connector which you will find under the carpet at the left rear strut tower. You should see somewhere close to battery voltage at the blue/green wire during cranking. If the reading is ok, suspect the pump. A pressure check should be done if the voltage is ok. If the voltage is too low with the connector disconnected from the pump, suspect the pump resistor/relay. If it is non-existent, suspect the circuit opening relay or wiring. It would be helpful to download the factory service manual/wiring diagram.

I wouldn't go with a Walbro on a n/a engine. The stock pump is perfectly fine for a street ported n/a and your exhaust setup.

NeCr0mStR

iTrader: (3)

Ok, so I have about 5 to 5.5 volts to the connector. So that would mean the resistor /relay is bad. Where is this connected? I will investigate but if someone can tell me before I find it.

NeCr0mStR

iTrader: (3)

Ok so I found a picture I have of when I was doing a bunch of engine bay work.

Can someone tell me if the resistor relay is one of the labeled items?

Thank you

scrip7

iTrader: (6)

It's located on a bracket behind the pass side headlight. Looks like this:

[IMG][/IMG]

NeCr0mStR

iTrader: (3)

Does anyone know what part number the relay is?

scrip7

iTrader: (6)

Before you get another relay you can verify it's bad with an ohm meter. when you disconnect the connector you will see 2 wires going to the resistor and 4 wires going to the relay. You should see .70 ohms to .94 ohms at the 2 resistor wires. Testing it will eliminate any resistance problems / poor wiring connections between the resistor and pump.

I had one fail on my '90 NA and I had 4 volts at the pump. It hesitated and bucked until I replaced my resistor. I picked one up on eGay pretty cheap. A forum member might have a good one on the cheap.

NeCr0mStR

iTrader: (3)

The one under the hood not the one under the dash?

scrip7

iTrader: (6)

Correct. It's the one circled in red in the engine bay pic. The top one.

NeCr0mStR

iTrader: (3)

Cool thank you. Got an email to my Mazda parts guy and he should be able to get me a price on it tomorrow and have it Friday for me. Maybe Monday at the latest.

HAILERS2

If you checked the volage while cranking the engine and saw only five volts or so, that is normal as apple pie. The starter turning over drags the voltage down til the starter is disengaged.

scrip7

iTrader: (6)

I referred to the FSM which states approx 12v during cranking (via the relay), 9-10 volts during normal driving (via the resistor), and 12v again during hard accel. The pump current doesn't go through the resistor during cranking. Obviously the FSM should have said battery voltage during cranking, and battery volts again during hard accel, This would include voltage drop during cranking and charging voltage while driving. I also recommended that he verified the resistor with an ohmmeter. His 5 volts when cranking is too low.

HAILERS2

Yeah, the five volts is a bit low (quite a bit i.e. two volts or so low), but I sorta "read into" what he was doing and suspect his battery is low, therefore the five volts during Start/cranking. No harm meant.

NeCr0mStR

iTrader: (3)

I made sure after cranking that I had 12 volt on the battery and it was a little above 12 volt so it was charged normal. Unlike so many who would crank and crank and crank thinking it would help somehow I knew right away with the way it acted that it was not getting gas or spark. The plugs showed normal carbon for a good spark, but they were dry as a bone so I suspected fuel is the problem. I know that the filter is good since it was replace brand new when I put in the motor, and there was no gas smell at all on the plugs.

I checked the resistance from c-d and its within specs but the e-f resistance is 0. I have checked with 2 multimeters. One shows like .10-.15 ohms and the other is showing no resistance.

So I am assuming that is the problem. Anyone want to dispute or let me know if I am doing something wrong.

http://www.badongo.com/pic/6473554

Here is a picture of the resistor, you can see its all rusty for some of it. It also makes some rattling noises.