5.0-5speedgt

Ok so I'm looking for some help/ideas on what's wrong with my mustang. It's an 89 5.0 5-speed and I just bought it with very little history known on it. At first it only started with gas or starter fluid and then would stay running bUT didn't like being under a load while driving. It would backfire and bog down. I checked the wires first and it looked like the 4&7 and 3&5 wire were crossed. I set them to where they should go and it just got worse. I was told the motor was rebuilt 10k miles ago and from what I have been told and can see it has an after market camshaft, cobra intake,70mm throttle body and I haven't measured the maf but I know that's been upgraded. Also ss headers and smog+ac deleted. Any ideas anyone wants to bounce off me would be great. I would love to get this thing running smooth soon before it snows a ton in Massachusetts so I can enjoy it. Thanks in advance people

Boss_Hotrod

Make sure you are using a correct firing order. The order 5.0l ho and 351w are different from a regular 302. The correct order is 1-3-7-2-6-5-4-8. Also get a fuel pressure gauge and check that. With the car being able to run on starter fluid you either have not enough fuel pressure or a vac leak causing the car to run super lean. Make sure there are no loose hoses anywhere.

5.0-5speedgt

So a little more info. The fuel pump wont stop priming and it has a built in gauge and it reads 16psi. When I picked the car up it was 22psi and when I drove it home it was 38psi. The gauge is plumbed into the Schrader valve on the fuel rail so could there be an issue with the regulator? I have the firing order set to the ho motor but because I just bought it I'm not sure yet on what exactly was done and I'm waiting for a list from the previous owner. I've heard multiple things that could cause the pump to consistently prime but I like to figure things out instead of replace parts until I've found it any ideas?

Boss_Hotrod

Should be at least 36 psi with the key on engine off. You've either got a kinked line, clogged filter, weak pump, or faulty regulator. Make sure regulator diaphragm isn't ruptured by removing vac hose and smelling for gas.

5.0-5speedgt

The lines look good I could see a clogged filter being an issue with bogging but if the pump is constantly running I would think it would eventually get to the high 30's. I was leaning a little towards the regulator but I noticed it's a performance one that is adjustable. I haven't tried to bring it up to a higher pressure but from what I know and have heard the pump is set to run for a specific amount of time on start up and not run until it hits a specific pressure. With all that being said I very heard the ecm could have something g to do with that. Ever experienced something like that? I'd hate to replace the computer without confirmation that it is the problem.

Because I haven't been able to get any info from the guy I bought it from tomorrow I'm going to reset all of the timing to TDC and make sure the distributor is set right. I know that's not the fuel problem but the only think I can do is start from the bottom and move up from there and double check everything. I'll start looking for another ecm at some scrap yards so if I need it I'll have it

5.0-5speedgt

Also I was told the fuel pump was new when I got the car. The last thing I want to do is drop the tank because it's filled right now and I'm not sure it's where the problem is. I guess if I have to its only like 15 gallons

5.0-5speedgt

UPDATE: I was just informed it may have a 289 block bored to a 320ci? It's now come to light that it's never really run right and the kid just drove it as is. I'm starting to think that I might have to tear this motor down and make it right that way. Anyone know how I would easily be able to check to see if it really is a 289 block or if it's a 302? I know the casting numbers would tell me but any info on the best way to find them and what I'd me look for