If you have a bad credit record, then it can be extremely difficult to borrow money. This is because lending money is a big risk and if you have shown in the past that you are not good at being able to make repayments or have never borrowed before, then a lender will worry that you will not be able to make their repayments.
However, some lenders, such as those that offer logbook loans, are prepared to lend to people without giving them a credit check. They will use other information to decide whether they want to lend to you or not. They will want you to have money coming in each month, to show that you have the means to pay back the loan. They will also want a vehicle to use as collateral. They will need you to prove that it is worth some money so they will need to see the MOT certificate and they will look up the value.
If you already owe some money on the vehicle, perhaps because you had a loan to buy it, then this will be taken in to consideration. It might be felt that you owe too much money on it or that it is worth a lot more than is left outstanding. If they feel it is worth more than you owe on it, then they will probably lend you about half of the difference between its value and what is outstanding on your vehicle loan. If you own the whole vehicle then they may lend you more.
It is important to make sure that you will be able to manage the repayments though. It can be tempting to borrow more money than you need, so that you can have a bit extra to treat yourself. However, the cost of borrowing that money is big and if you cannot afford the repayments the fees and interest are even higher. So make sure that you are taking on a loan amount that you can manage. You need to be able to pay it back and if you lose your job, then you will still have to find the repayment amount each month, so bear that in mind.